The movies have gone through a tremendous change in the past few years. Of all the styles and stances available to filmmakers, just two - escapism and introspection - have come to dominate the screen.
Escapism is rampant in the blockbusters, from ''Star Wars'' and ''E.T. the Extra-Terrestrial'' to ''Ghostbusters'' and ''Gremlins.'' Introspection marks the more prestigious productions, on the order of ''Tender Mercies'' and ''Under the Volcano.''
Escapism and introspection have long been Hollywood staples, of course. But they haven't always commanded the movie scene as thoroughly as they do now. Just a decade ago, Hollywood didn't hesitate to arouse, challenge, or even politically provoke its viewers - not all the time, but startlingly often by current standards.
That's because the '70s were a time of political and social awareness in movies. Even mass-audience productions tackled meaningful subjects that would drive most of today's filmmakers into hiding at the nearest video arcade. Look at the output of 1974 alone, which gave us not only ''The Godfather Part II'' and ''The Conversation,'' both by Francis Ford Coppola, but the political thriller ''Chinatown,'' the Vietnam documentary ''Hearts and Minds,'' and the tortured conspiracy theories of ''The Parallax View,'' with Warren Beatty.
Why are the '80s obsessed with trivia like the Indiana Jones pictures? Why are serious films more preoccupied with personal problems than with broad issues?
And what happened to the time when Hollywood news didn't revolve around the nastiness of the latest special effects, but focused on the sociopolitical comments of movies as varied as ''Apocalypse Now,'' ''M*A*S*H,'' and ''The Deer Hunter''?
Some provocative answers can be found in a welcome new book called ''Hollywood Films of the Seventies'' (Harper & Row, $9.95) by film journalists Seth Cagin and Philip Dray. They note that Hollywood echoes its capitalist underpinnings by passing through cycles of boom and bust. They add that ''bust'' periods often coincide with technological changes, as when the rise of television in the 1950s polished off the traditional Hollywood studio system.
Our current binge of escapism and introspection marks another such period, say Cagin and Dray, as new video systems make inroads on theater attendance. Also important is a deeper, but related, phenomenon: the fragmentation of American society in recent years. I agree with this view. Although the authors don't pursue their argument quite this far, it seems logical that the self-obsessed ''me generation'' should find its way to a technological boom centered on private, homebound entertainments. Cable-wired TV sets, video games, and cassette movies are enormously different - culturally and psychologically - from a social, community-related activity like traveling to a neighborhood movie house.
Theatrical films are still a going enterprise. But they are expensive and must promise to attract sizable audiences if they are to be made and distributed. Hence the flight away from risky projects, unsettling subjects, and controversial comments. Hence also the explosion of films aimed at special groups: flighty fantasies for teen-agers, sex farces for young adults, and so on , which ignore the tastes (and even the scruples) of older audiences to a degree unthinkable a few decades ago, when most movies were targeted as broadly as possible.
Cagin and Dray go too far when they call the late '60s and early '70s a ''golden age'' of political cinema. As they acknowledge, the counterculture upheavals of that period contributed a lot to the fragmentation of today. Then, too, plenty of bad films were foisted on viewers under the banner of sociopolitical probing. Sensationalism reached new heights. (Even this book is subtitled ''Sex, Drugs, Violence, Rock'n'roll, & Politics.'') And alongside laudable pictures like ''Coming Home'' and ''Nashville'' were reprehensible tracts like ''Joe'' and ''Death Wish.''
In their thoughtful analyses of key movies, though, Cagin and Dray point up the important fact that many '70s films - popular, widely seen pictures - do stand up to thoughtful analysis, as reflections on issues and as artfully realized works in their own right.
The blame for today's movie blandness goes partly to the habits and mind-sets of viewers. And it also goes to the latest generation of filmmakers. Though steeped in film-school education and technical adventurism, many are so limited in outlook that their movies aren't about life, but about other movies, fondly remembered and relentlessly rehashed. If the '70s weren't really a golden age of film, they were a lot bolder and more willing to explore the trickiest ideas. Some of their feisty spirit would be a welcome addition to the current scene.