NEW YORK — I speak now as a die-hard theater marathoner — one of the congregants who answered the call of Peter Brook and melted into the cosmic universe of “The Mahabharata”; who sat through 12 hours of Robert Wilson’s “Life and Times of Joseph Stalin,” lost in stoned contemplation of the infinite shades of the color blue; who spent a whole day enthralled by the physical transformations wrought by Trevor Nunn and John Caird for “The Life and Adventures of Nicholas Nickleby.”Last week, I felt the old urge again and went to see all three plays in Tom Stoppard’s epic trilogy, “The Coast of Utopia,” over the course of one glorious day and night at Lincoln Center — and this nine-hour event convinced me that marathon playgoing could be the salvation of modern theater. Lest we forget, live theater is a communal experience rooted in ritual and magic and, when the high priests know what they’re doing, capable of transporting the participants into a state of ecstasy. That’s the way it was in ancient Greece and Rome, when thousands would gather in outdoor amphitheaters to laugh and cheer and weep over the fate of kings. And that’s the way it was at the Vivian Beaumont Theater, when an alert and noticeably eager audience lifted its eyes to the stage in full expectation of being awed by Stoppard’s sweeping views of Russian society during the tumultuous era of the mid-19th century. If there’s one thing missing from today’s incredible shrinking theater, it is that sense of awe. Shows are condensed into 90 minutes; casts have been downsized, orchestras minimalized; and intermissions are a thing of the past. But the chicken-and-egg conundrum surely applies here, since the new streamlined forms seem built to accommodate the narrow scope and limited content of most plays. Which is not to say slim-and-trim plays can’t be engaging, entertaining and even provocative. But you can’t call them awesome. That takes size — and size means vision. Taken individually, each of the three plays in “The Coast of Utopia” is a powerful work, and each has been brilliantly mounted by director Jack O’Brien to maximize its particular strengths. Key images say it all: the hordes of anonymous serfs conveying the inhuman conditions of czarist Russia in “Voyage,” the magnificent crystal chandelier signifying the enlightenment of Paris in “Shipwreck,” the junkyard of blackened objets d’art symbolizing the collapse of civilization in “Salvage.” But it isn’t until all three plays are viewed together that the scope of Stoppard’s vision can be fully appreciated. Call them whatever you will, and argue over their relative merits if you must, but the separate dramas are really individual movements in a single work of epic scale. Audiences at the so-called marathon performances get it. They don’t have to worry about distinguishing one Bakunin sister from another, or struggle to recall whether George Herwegh is a poet or a playwright, or wonder what Karl Marx has to do with that ginger cat. While they might miss pieces of the story, what they get is a clear sense of the drama’s historic arc — and the full force of Stoppard’s vision. More than that, though, what audiences get from a marathon event like this is the all-too-rare experience of participating in theater the way it was meant to be, a communal engagement with a living art. So, please don’t confuse this near-religious experience with watching back-to-back season episodes of “Lost.” To put it more prosaically, you could feel the joy in the air at the performance I saw. Audience members were all dressed up and downright giddy as they gathered in the lobby and outside the Beaumont during intermissions and dinner breaks. Confounding assumptions about the supposedly senior demographic of Lincoln Center subscribers, this crowd was a cross-section of New Yorkers that any producer would kill to get into his shows. Young, old and in-between, people were actually partying in their seats before the lights went down — and I didn’t hear a single cell phone for nine hours. Going into the theater, couples greeted one another like guests at a wedding reception. In the lobby at the first break, a strong contingent of theater people hailed their peers and air-kissed like crazy. A teenager grabbed a seat at the edge of the pool after “Voyage,” studiously consulting his notes for “Shipwreck.” And one lady with a walker all but sprinted across the plaza from nearby eatery O’Neal’s to get to her seat for “Salvage.” So much for the fabled ennui of New York theater audiences. This crowd was pumped. And don’t think the cast couldn’t feel it from the stage. Like all of O’Brien’s exquisitely choreographed ensemble bows, the curtain call was a thing of beauty and quite special, since the players did not come out for bows after the first two plays. But this time, the performers looked out at the cheering audience and applauded back, engaging us all. A radiant Martha Plimpton flung open her arms. Scott Parkinson, who stepped in as understudy for Billy Crudup in the role of Belinsky, hopped up and down, grinning madly. So, did we “get” Stoppard’s dramatically complex and intellectually dense work? You bet we got it — and we didn’t want to let it go.