NETWORK TELEVISION has long operated according to the principle that even though too many cooks may spoil the broth, they at least make it easier to spread the blame. The point is made with deadly eloquence by a pair of current TV fiascos: the ABC prime-time news magazine "20/20" and the NBC daytime talk show "America Alive!"

There are lessons to be learned from both of these shows and one of the infuriating and hilarious things about television is that even if broadcasters do learn them, five years from now they'll be ready to make the same mistakes all over again. TV is a slave to the short attention span in more ways than one. It's the greatest recycler of retreads in history.

Comparing "20/20" and "America Alive!" is certain to irk the staffs of both shows.ABC News has serious journalistic aspirations for "20/20," or so spokesmen insist, and in truth, once the program's playful pratfall of a premiere was out of the way, "20/20" went on to hit a few hard-nosed highs, including overlong but unblinking reportage on the Ford Pinto fires and, more recently, a two-part shocker about FBI informants in the 1965 civil other hand, only wants to be a cuddly dog for the national lap; a pert little pick-me-up at midday and a newsy, folksy alternative to soap operas and game shows for daytime viewers, most of whom are women.

What both shows have in common is that they are failures.

At "20/20," there are not only too many people wearing aprons, but many of them have been running around the kitchen brandishing meat cleavers and shouting "Zut alors!" The population decreased by one this week when executive producer Bob Shanks resigned. Part of the reason had to be that ABC News and Sports President Roone Arledge had brought in another cook, Jeff Gralnick, to supervise Shanks, even though Shanks had vice presidential status in the news division.

As a result of Shanks' exit, the program will probably veer more in the investigative reporting direction of the CBS blockbuster "60 Minutes," but it remains to be seen if Arledge and company can pull this off effectively. Disgruntled insiders at ABC News - Arledge has referred angrily to them as "dissidents" - say some of the investigative pieces so far have been sloppy and disorganized or old hat and tired. They decry the use of qualifying disclaimers like the one reporter and fashion plate Geraldo Rivera added last week after the first of two reports on lingering effects of the defoliant called dioxin, or Agent Orange, used in vietnam.

Rivera seemed to be presenting evidence that some American G.I.'s exposed to the substance during the war have developed cancer symptoms since. He quoted authorities, he interviewed victims on film, and then at the end of the report, after systematically building up a case, Rivera suddenly added that "in fairness" to the companies that manufacture dioxin, the causal link had not been established absolutely beyond doubt and "conclusively." And yet, though Rivera didn't say so, a link between the defoliant and cancer had been reported as far back as 1973. In 1977, the Environmental Protection Agency labeled dioxin "perhaps the most toxic small molecule known to man."

The Rivera disclaimer served to negate the whole thrust of what had just been laboriously reported on the program. But one problem with all of Rivera's reports is that his tone of voice and style of delivery are so strident, melodramatic and moralistic that it's almost impossible to become involved in what he is saying or to take it sriously, anyway. He is to journalism what the Rockettes are to modern dance; he always comes out kicking.

Like much of what is seen on "20/20," the dioxin segment was woefully overproduced; Geraldo's infamous quarter-hour expose on jackrabbit maiming, which began the first show, was originally supposed to be a three-minute piece, but it got liberally seasoned with money and hokum. At the beginning of the dioxin report, on camera, a Vietnam veteran declared, "I died in Vietnam, and didn't know it." Fascinating. We wanted to hear more. We wanted to learn about this man. But he was instantly abandoned by the report and soon we were dallying in Italy with Geraldo as he gathered support for an argument that he would later say wasn't very conclusive anyway.

The producers of "20/20" appear utterly unaware that one of the glorious possibilities intrinsic to television is its capacity to make the abstract particular and to turn impersonal stories personal; statistics about men dying are almost meaningless on television, but one man talking about his terminal illness to the camera can be incomparably affecting.

It's too many cooks and too many ingredients that turn so many "20/20" stories into production numbers instead of confrontations with a reality, or an issue, or an outrage. But to judge from stories that have come out of ABC News about bedlam prevailing at "20/20," it may be a wonder that anything of worth has made it to the air. There are tales of reporters and producers being thrown out of editing booths, of last-minute alterations done by Shanks and Arledge, of a general air of know-nothingism in which serious journalists fight to maintain their dignity.

It is widely assumed at the network that if "20/20" fails, Arledge may be out as news director and back to the no-quite-so-wide world of sports. Arledge himself has said that he considered delaying the premiere of "20/20" because he feared negative reaction to it would slop over onto his recently revamped evening news show, "World News Tonight."

Hard-core journalists at "20/20" got a slap in the face when Arledge hired Hugh Downs, one-time fall-guy to Jack Paar, as the program's anchor after Harold Hayes and Robert Hughes were handed their chef's hats and sent packing. ABC publicity describes Downs as the "distinguished television reporter, newscaster and program host." Reporter? Of what? Newscaster? When and where? The idea that journalists like Sylvia Chase, Sander Vanocur and Dave Marash have to report to Hugh, on the air, like school kids trotting up to the teacher's desk is preposterous. Downs is a pitchman and pacifier, the program he's better suited for is "America Alive!"

NBC's new odds-and-ends show premiered last week with a daily parade of insipid tidbits built around the central theme of vacuity. The fact that the program is visually a mess and packaged about as attractively as Godzilla should be a true embarrassment to NBC, where "The Today Show," with a similar format, has for years outclassed all competition and, after undergoing a general editorial rejuvenation, has shown a new industriousness and even charm in recent months.

"The Today Show," produced by Paul Friedman, proves that there can be life even in institutions and that hard news can live on the same video plain as soft-info and entertainment and not be contaminated or compromised.

But Woody Fraser, producer of "America Alive!," does not have a deft touch when it comes to mixing elements, and the elements he chose to mix indicate a rapacious reluctance to innovate. To host the show he lured Jack Linkletter out of a well-deserved retirement from television; Linkletter has the kind of smile that wilts plastic flowers and a penchant for phrases like "super nice." Combining this with a bouncing Bruce Jenner, grinny granny Virginia Graham, perky Pat Mitchell, and a third-rate imitator of Rex Reed named David Sheehan, "American Alive!" suffocates on its own desperate frivolity. It becomes "America Asleep."

The fact that much of "America Alive!" is live sounds promising, but the interviews are so pre-planned and the features so prepackaged that the program never seems remotely spontaneous.

That may be why Fraser has the word "Live!" flashed on and off at frequent intervals during the program. Twenty years ago, when nobody bothered to put exclamation points at the end of such words, NBC broadcast a live hour of light entertainment and chit-chat, "Club 60," out of Chicago, five days a week, and it was fresher and brighter by a mile than "America Alive!" The featured singer on the show, by the way, was a jaunty Irishman named Mike Douglas.

It says something about the mentality behind the program that although it makes a big deal out of romping from city to city, the cluttered hodge-podge that passes for a set in the New York studio prominently features an artificial Manhattan skyline - even with real thing within camera's reach.

So what happens? Why do TV programs that sound good on paper turn into confetti when they make it onto the air? Partly because too many people hire too many other people as scapegoats, partly because a new idea rarely gets a nod unless it reminds some executive of a familiar old idea, partly because a good number of the people working in television do not know what they are doing, and partly because the hyped-up competition that results from network TV's escalating profitability means that people are more afraid than ever of risking their jobs or their reputations on a truly novel and trailblazing brainstorm.

By the time a TV program gets to the air, panic can wear it down to an impotent frazzle. When you watch it you can almost see all the surgeons - to switch metaphors for a moment - working feverishly on the body. They cut, they stitch, they add and they subtract. But the patient may die anyway, or at best, go into a catatonic trance. One looks into its eyes and realizes there's nobody home.rights killing of Viola Liuzzo.

"America Alive!", on the