MOSCOW - After three years of living in Moscow, it would be relatively easy in a farewell piece such as this to tell you all that is wrong with the U.S.S.R., to rehearse once again the inefficiencies and inequities of the Soviet system.But if Americans know anything about the Soviet Union, we probably know what is bad about it.

Instead, I'd like to suggest something of what I think is wrong with us.

That may seem an odd way of rounding out a tour as a Moscow correpondent, but my point is precisely that we have tended over the years to dwell so much on the very real shortcomings of the Soviet Union that we bear a deep hostility toward this remarkable and confounding country - which doesn't do us any particular good and in a nuclear age could lead to catastrophe.

We recognize a great deal in the United States that is evil - crime, racism, poverty, injustice - and yet we don't conclude from such glaring faults that we are all bad.

It is, the same token, a mistake to conclude that, because there is so much in the U.S.S.R. which we find repugnant - the lack of free expression, the self-righteousness and hypocrisy of the ideology - the whole system is rotten.

As seen from here, though, Americans are so suspicious of Soviet political motives that, aside from the ballet and making weapons, they don't think Russians are good for much.

The phenomenon is hardly a new one. Twenty years ago, Harold J. Berman, then as now a scholar of Soviet law at Harvard, wrote a memorable essay he called "The Devil and Soviet Russia." In that era of Sputnik supremacy is space, when Americans were suddenly alarmed about the successes of Soviet science, Berman's contention was that we had become so fixated on the evils of communism that we were not prepared for its achievements.

If Russia was really as bad as we imagined it, he wrote, "with 20 million prisoners in Siberian labor camps, workers ground down by management, every tenth person an informer, people afraid to talk about anything," then we in the West should have nothing to worry about: "Such a system could not survive a single major crisis."

In fact, said Berman, "The Soviet system which has been created is quite different. It is a working totalitarianism . . . It is a system that gives promise of achieving the very goals it has set for itself: economic security, political power and technological progress - by the very means it proclaims: absolute subservience to party discipline and the party line."

The professor was right. For all the continuing backwardness in some rural areas and a general living standard that is still far below that in the West, the U.S.S.R. today is unquestionably oen of history's imperial giants. The Kremlin new presides over the world's second largest economy, the biggest in terms of critical energy output. It has a mighty military machine and dominates an alliance that the Pentagon would have us believe is stronger in many respects than our own. And Moscow today wields formidable political influence on events in every corner of the globe.

There was truth as well as pure bombast in the speech Leonid Brezhnev made last month when he presented a new national constitution to the party's Central Committee.

"The capitalist encirclement of the U.S.S.R. exists no more," he declared. "Socialism has turned into a world system and a mighty socialist community has formed. The position of world capitalism has been substantially weakened. Dozens of young states, former colonies, are coming out against Western imperialism."

Considering this is a country that, as every Russian will tell you, was ravaged by revolutions, invasions and terror for most of the century, the record is certainly impressive. That much in recent years has come to be officially recognized in the United States - at least it was in the previous administration.

"The issue of how to deal with the Soviet Union has been a central feature of American policy for three decades," Henry A. Kissinger declared in a major pronouncement on the subject in February, 1976. "What is new today is the culmination of 30 years of postwar growth of Soviet industrial, technological and military power. No American policy caused this no American policy could have prevented it . . .

"Coping with the implications of this emerging super-power," he added, "has become our central security problem."

KISSINGER'S solution was detente (he wasn't the first to come up with the idea, but he was the one to get it implemented). Detente, as the French writer Andre Fontaine neatly put it, was not the same as peace or else it would have been called peace. It was an arrangement whereby a combination of political, military, technical and commercial agreements were reached for the expressed purpose of preventing the sort of confrontation that would end in mutual annihilation. For a time, roughly between the summers of 1972 and 1975, the process was working. To borrow from Chairman Mao, a hundred flowers bloomed.

I have watched detente unravel since then to the point where virtually all that is left is a batch of yellowing declarations of good intentions, essentially meaningless in a real crisis, and the strategic arms limitation talks that are a lot further from success than any reasonable person would want them to be.

The Kremlin reviles Jimmy Carter, calling him a "demagogue" in his domestic policy who supports "absurd and wild concoctions" about Soviet abuses of human rights and who seeks "unilateral advantage" for the United States in the arms talks. Carter says people shouldn't get rattled every time Brezhnev sneezes.

Two-way trade is stafnant and hardly anyone here holds out much hope for improvement, let alone billions that were once talked about. Cultural and scientific contacts are mostly cosmetic. For the first time in years, an American diplomat and journalist have been expelled. Others have been severely harassed.

Where have all the flowers gone?

There are, of course, a multitude of explanations for what were wrong. On my list are: A) Detente was over-sold by Richard Nixon in an effort to distract attention from Watergate, and then disillusionment set in; B) A powerful alliance of security-minded conservatives and human-rights liberals in the United States whipsawed Kissinger as alternatively soft and cynical; C) The Soviets, being Soviets, pressed for advantages in places like Angola (where they succeeded) and Portugal (where they did not), thereby cutting the ground out from those in Washington who contended that Moscow would act responsibly; D) Military-industrial lobbies in both countries went on pursuing their vested interests in expanded outlays for defense.

I leave it to geopolitical pundits to assess the strategic implications of issues like C and D. The arguments I want to stress here are more the matters of attitude. A and B. It was, unfortunately, I believe, American antagonism to detente, those endless debates over one and two-way streets, whether we were duped in this deal or that, which was instrumental in its eventual collapse.

WE HAVE so deeply ingrained an aversion to godless Bolshevism, going back for as long as the Communists have been around, that we seem incapable af accepting that the Russians can ever do anything positive, except for the occasional talent or goodwill of individuals.

As Berman was saying two decades ago, the fact that this is a system we do not like does not mean that it is totally bereft of virtues.

"It is a false conception of evil," he wrote, "which assumes that men who believe in evil doctrines - such as doctrines of world revolution or the dictatorship of the proletariat - cannot at the same time work to accomplish great humanitarian benefits . . . For example, under the leadership of the Communist Party of the Soviet Union, the number of doctors in Russia increased from about 20,000 in 1917 to about 300,000 in 1957 . . . and, under the same leadership, illiteracy declined from over 50 per cent to less than 5 per cent."

The Kremlin's firm and often harsh control has made it possible to mobilize the resources for transforming places like Kazakhstan in Central Asia, Dahestan in the Caucasus Moutains and Yakutia in Northeastern Siberia from the widls they were merely two generations ago, remote lands of nomads and exiles, into modern societies. After all, vast areas of the Soviet Union were total undeveloped at the time of the revolution. But today, for instance, Yakutsk, the capital of Yakutia, has a population of 150,000, high-rise apartment buildings, theaters, a university - all that in winter temperatures often more than 40 degrees below zero.

Yes, the U.S.S.R. is an empire run from Moscow and outright nationalism is not tolerated. Nonetheless, such ancient peoples as the Armenians, Georgians and Uzbeks retain amazingly strong local identification and character. What they have lost in autonomy, small and often embattled nations like Armenia have gained in security. They have a language, their culture, even their own church. Communism has been imposed on them, but it not crushed them.

Even in the most enlightened of philosophies good and bad are intertwined. Berman again: "Did not Cromwell, the great restorer of English liberties, treat the Irish with barbaric cruelty? Did not Americans who fought for the inalienable rights of 'all men' at the same time buy and sell slaves?"

Turning the reasoning around a bit: Is it not conceivable that the same Soviet leadership which so severely restricts free expression at home and seeks ever greater influence abroad might genuinely want to improve its peoples' lives, might genuinely want a measure of mutually beneficial cooperations with the West, might genuinely be committed to preventing a nuclear holocaust?

The way it has looked to me from here, Americans more often than not say no.

Partly, we may be negative because Kremlin ideology is so infuriatingly bumptious, demanding credit that is not deserved and asserting achievements that have not been attained. Because the Soviets so aggressively insist that they are perfect, we instinctively want to counter with their flaws.

In the early 1970s, when the Kremlin began to allow tens of thousands of Jews and other minorities to emigrate each year, it proclaimed that anyone who wished to go could do so (except for those with state secrets, who would have to wait a few years) and that no one who tried to leave would be harassed. It was obvious to Americans that those assurances were false. Hundreds of Jews lost their jobs, some were drafted into the army, others were jailed.

So, instead of concentrating on how much the door had been opened - in 1973, about 35,000 Jews left - we focused on how closed it still was. Finally, the Soviets got fed up with the controversy, claiming that their humanism was not appreciated. The rate of Jewish emigration, at least, is down by more than half.

BUT SOMETIMES it has struck me that our suspicions were exaggerated.Take the case of the 1975 Apollo-Soyuz mission when Russian and American spaceships linked briefly in orbit. On the eve, an article by a space expert published on The Post's editorial page reamed the exercise, comparing it to the 1972 grain deal in which the Russians suckered American traders. The expert's contention was that the Soviets were benefitting by access to our advanced technology while the U.S. side got nothing.

The way it looked from here, the United States got valuable first-hand exposure to the Soviet space program and examined its intricacies and shortcomings, which we found to be many. But even more importantly, the mission was the occasion for a tremendous outpuring of good will toward the United States. "The Apollo-Soyuz project," said an article in an important Soviet journal, "is a symbol of the changing relations between the U.S. and the U.S.S.R."

Many ordinary Russians were emotional. I listened carefully as they watched the blastoffs on television, clustered at store windows, in offices and homes. Invariably, the comments centered on the excitement of such cooperation and how it might mean the countries would get along more easily.

"It makes me feel better," said a World War II veteran, a man I know well and who keeps a very cool eye trained on what the Kremlin does, "to know that old allies can work together instead of always trying to outdo each other." Treacly, perhaps, but sincere.

I had to fly to Washington the next day, so it was there that I watched Apollo maneuvering into position for docking with the waiting Soyuz. "At last," cracked someone in the group gathered around the TV set, "we found a way to stick to it the Russians." Everyone else guffawed.

WE ARE ALSO condescending about some things the Soviets do well. The example of literature has fascinated me. It is a very rare American who could name any contemporary Russian author besides Alexander Solzhenitsyn - and he is better known for his political dissent than his novels. Yet there is a very active literary life here: People like Yuri Trifonoc, Valentin Rasputin, Vasily Belov, Alexander Vampilov, Vasily Shukshin, Chinghiz Aitmatov and Fazil Iskander are greatly admired by the intelligentsia and write with style and insight - even if they do battle the censors behind desks and in their heads.

Two years ago, when I wrote a long article about some of these authors, the headline given by an editor was "The Writers Who Stay," as if anyone of worth should be expected to leave.

For all the well-known restrictions on Soviet cultural life, it is a fact that a sophisticated Russian knows a great deal more about our contemporary fiction than we about theirs. "Anywhere that people like to read," as one Russian put it, there are fans of Faulkner, Baldwin, Salinger, Vonnegut, Updike, Albee, all of whom and others have been expertly tranlated.

We like to believe that our literature must be better than theirs because it is unfettered. But that should not impose ideological blinders on Americans which prevent us from taking what the Soviets do at its true worth.

The Soviet Union is a closed society, but it is not nearly as closed in many ways as it used to be. For over three years now, since jamming ended, millions of Russians have listened to the daily broadcasts of the Voice of America and the BBC. It is no longer even considered daring to do so. Russian young people, even in the countryside, pattern themselves increasingly on the casual, blue-jeaned and rock music styles of their Western counterparts. Hundreds of thousands of sportsmen and visitors will be steaming into Moscow for the 1980 Olympics, another big hole in what was once truly an Iron Curtain. Always lurking somewhere, crude and vicious, are the men from the KGB security police.

But the KGB is not everything.

WELL. THEN, you may fairly ask, how do I think we can make our attitude toward the Soviets less reflexively hostile?

That is a very tough question for which I have no all-encompassing answer. We should try, in keeping ourselves informed about what is happening here, to separate the real advances in Soviet economic and social life from the ideologically inspired claims - pro and con. We should try, of course, to continue expanding contacts in scientific and cultural fields that slowly grind down barriers to understanding. We should be, perhaps, more skeptical of what dissidents say because, with a cause to plead, they cast matters in the most apocalyptic light.

Changes obviously can come about. Remember how menacing the Red Chinese seemed only a few years ago?Then came the Nixon trip to Peking in 1972 and a slew of what in retrospect were naive reports on the dignity and purity of Chinese life. Today, we probably have a more realistic view of China than of the Soviet Union, although we know less about it.

So far, 1977 has been a terrible year for Soviet-American relations. A freeze like that, it seems to me, encourages just those repressive influences in the system that we find most abhorrent. The current crackdown on dissidents, the most extensive in this decade, would be harder for the Kremlin to undertake if Moscow's vested interest in good relations with Washington were greater.

Lev Kopelev, a wonderful man, a writer now 65 who spent a decade in Stalin's prison camps and has been harrassed again in recent years for his outspoken defense of human rights, put the situation so eloquently in an interview not long ago that I'd to repeat it.

"I sympathize with your President Carter in his support of human rights," Kopelev said. "I think that he is a good and sincere man. There is at last a politician who puts together politics and morals. But I think that in his tactics, especially with our country, he makes mistakes.

"He is too straightforward, too direct. He doesn't understand the special nature of our society - not Communist or Marxist traditions, but Byzantine, Oriental conceptions of prestige. If I were to advice Carter how to help us," he chuckled, "I would say, 'Be firm in your convictions but, at the same time, offer some golden bridges. Make it so that our side can come to you without losing prestige.'"

He added with a sigh: "If now starts again, the Cold War it will be worse for us, for all our people."