Mediocrity triumphed over quality on our 1980 theater front. What's more disheartening, chaff was too often mistaken for wheat.

Nearing its 10th anniversary, the Kennedy Center seems to have lost its bearings. In January, it appeared to have formed an alliance with The Acting Company, created from his Juilliard graduates by John Houseman. The next month Roger L. Stevens, the Center's chairman, announced yet another alliance with New York's Joseph Papp. In November, there came an announcement of the Kennedy Center Musical Theater Group. In December, it was reported that next year the Eisenhower Theater would have its own resident acting company.

For conspicuous mediocrity there was the midsummer booking of "Richard III," which featured an absurd performance in the title role by Michael Moriarty and a wholly unintelligible one by Viveca Lindfors, swathed in cigar smoke, as Mad Margaret. This wretched production already had been unveiled at Connecticut's Stratford, and the Center should have been too proud to have it on the premises.

How can one account for the two "plays" by Tina Howe, "The Art of Dining" and "Museum"? Howe has an ear for dialogue but no sense whatever of a narrative line. In the prime of vaudeville these may have made amusing 20-minute sketches. Our theater is in a sorry way to think of these trifles as plays.

There are, to be sure, perfectly clear reasons for some of the Center's disasters. It has to book something : A dark house is a total loss. And theatrical economics have become a nightmare. Nonmusical play budgets are nearing million-dollar launchings. And in musicals -- where the lowliest member of the chorus can cost close to $800 per week because of fringe and per-diem expenses -- budgets have hit the $2-million mark.

Union power is a growing consideration. It was reflected recently in the costs of having the sets of "Sweeney Todd" moved in full view of the audience. To further the illusion of 19th-century London, the stagehands were asked to wear caps. The 18 stagehands did so -- at an added cost of $25 each per performance, according to producer Richard Barr.

The result is that fewer productions are touring, which explains Stevens' decision to try a resident company, a la Arena Stage, for the Eisenhower next season. It's an idea Stevens had years before the Center's construction was even started: In a Georgetown living room long ago, Hume Cronyn and Jessica Tandy promised to be part of such a company. After all the fits and starts, outlined above, maybe this really will happen. But it will have to go some to equal Arena Stage.

Some of the year's disappointments were at least on a professional level. Who could have foreseen that Stuart Ostrow would lose his way so catastrophically as he did with "Swing"? It was clear that producer Elliot Martin should have foreseen rewrites would be needed on Tennessee Williams' "Clothes for a Summer Hotel." But Williams was not the only one of our major playwrights to trip during 1980. Edward Albee's "The Lady From Dubuque" wasn't ready either, and perhaps too much tinkering was done with Arthur Miller's "The American Clock."

The Shubert Organization's reentry on the Washington theater scene is decidedly good news, as its lavishly mounted, gloriously played "Amadeus" at the National Theatre showed. With three more proven productions to come within the winter and spring seasons -- "They're Playing Our Song," "Children of a Lesser God" and "I Ought To Be in Pictures" -- the National is on the road back to health. Within the year, full-scale renovations should make the old house sparkle.

Having inspired Rex Harrison to revive "My Fair Lady" and Richard Burton to go back to "Camelot," Yul Brynner is about to get to the Warner in his long-lived resuscitation of "The King and I." It is too early to tell exactly how this will look on the Warner's relatively limited stage; but the Warner's effort to find a new life is certainly dynamic. If its most solid success for two separate runs is rooted in its sleazy title -- "The Best Little Whorehouse in Texas" -- at least that title has served three concurrent companies well, thin gruel that it be.

The departure from the Senate of North Dakota's Milton R. Young focuses attention on Ford's Theater. His 1948 legislation provided that the building's restoration as a museum would imclude full facilities for live performances. That was nearly 20 years before the house was opened under the direction of Michael Dewell and his National Repertory Theater. Though efforts are constantly made to rewrite this history, it was Sen. Young who turned Ford's into a working theater. With its erratic policy of booking, Ford's must be ranked as the city's most mediocre theater.

The most exciting, creative and reliable theater in town remains Arena Stage, now celebrating its 30th anniversary. It is the forerunner of every other theater in town, including the future Eisenhower. Its policy of resident players and subscription audiences has been followed, not always as well, by the defunct Washington Theater Club, the Folger and, next season, the Eisenhower.

Arena's year included acting standards rarely reached at other theaters, notably Richard Bauer and Stanley Anderson in "Emigre" by Slawomir Mrozek, Pat Carroll's superb "Gertrude Stein, Gertrude Stein" and the richly staged "Galileo."

The Kennedy Center's Terrace Theater proved a happy home for P.J. Benjamin's performance in "Charley and Algernon," and it seems to have developed a viable relationship with the Folger Theater Group. But the finest Terrace productions have been those of the Opera Society, immensely energized by Martin Feinstein.

Finally, The New Playwrights' Theater continues its sometimes noble experiments, and there are high standards in Joy Zinomon's Studio Theater, modest, creative places both.

There were some classy events in 1980. Vivid David Merrick brought, along with some old tunes and styles, excitement with "42nd Street," and the Tony awards went to worthy productions, "Evita" and Jim Dale's "Barnum," yet to be seen here. And, in New York Richmond Crinkley has relighted Lincoln Center's Beaumont.

The year had its irreparable losses. There'll be no more Richard Rodgers melodies, and Gower Champion's death the day "42nd Street" opened in New York will be part of that musical's lasting mystique. Nina Vance -- creator of the Houston Alley Theater, part of the vanguard in the regional theater movement -- will be remembered far beyond Houston; and, more than a year later, I still miss Preston Jones. Two influential critics died, Kenneth Tynan and Harold Clurman, and three New York theaters are about to be torn down -- the Helen Hayes, the Morosco and the Bijou. Is it too much to hope that the one to replace them in the new Portman Hotel will be more like the Hayes and Morosco than the Uris and the Minskoff?

Quality, as Barbara Tuchman pointed out recently, is getting rarer and rarer. With some happy, perhaps accidental exceptions, mediocrity was the theatrical level for 1980.