Lately, the idea of a Steven Spielberg has felt endangered. For more than 50 years, his imagery has epitomized American movies, maybe even epitomized America. He has been at the center of an industry that, if it’s not dying, is certainly diminished. The sort of original movies that made Spielberg Spielberg are virtually nonexistent, even though the two major flavors that now define the industry — global box-office smash and best picture nominee — are, with Spielberg, indistinguishable (start with “Jaws,” “Raiders of the Lost Ark,” “E.T. the Extra-Terrestrial”). More than once, he inhabited both modes within one calendar year: “Jurassic Park” in the summer of 1993, for instance, then “Schindler’s List” at the end of Hanukkah, perhaps the most triumphant single-year change-up any Hollywood director has had. (He’s still the most commercially successful director ever, and he’s tied, at 13, with William Wyler for directing the most best picture Oscar nominees.)

Popular art has always bonded us to one another, no matter what might have been cleaving us apart, no matter how different our lives or how our responses to that art diverged. And Spielberg’s films have been a premium adhesive. Not only the ones he directed but the dozens of swooshing, indelibly kooky hits unleashed by Amblin Entertainment, his production company: “Poltergeist,” “Gremlins,” “The Goonies,” the “Back to the Future” trilogy, “Who Framed Roger Rabbit,” “Arachnophobia.”

Spielberg’s stardom arose from the collision of capitalism, audacity and creative vision. His movies emerged alongside the arrival of cable television and proliferating advances in personal computing and home entertainment. I watched “E.T.” at the movies, devoured it on cable, played it on my Atari and let Michael Jackson sing me a lullaby the movie inspired him to write. (Spielberg: so titanic that the other king of pop worshiped his thrillers.)

But a kind of cultural malnourishment has set in. While you once needed a pair of hands to count the major studios, we’re on the verge of barely needing one. And the best, most lucrative ideas entail microwaved nostalgia that we all know by its legal nickname: I.P. The takeovers and reheating, the obscure metrics that ensure we never quite know exactly how popular anything is, it’s dispiriting: Pac-Man eating ghosts, algorithms keeping secrets.

When movies play in only a handful of theaters to qualify for awards, and increasingly millions of us watch them on our phones, “that is not my definition of a motion-picture experience,” Spielberg told me. For that, he said, you need “an audience to be the accelerant of that experience, to be the contagion of making the experience even more profound for the individual in that crowded theater — or what we hope is a crowded theater.” Obviously, streaming changes that experience, denying us the companionship of hundreds of strangers either confirming or causing us to question our humor, our tastes, our responses.

This is to say that what Steven Spielberg symbolizes, what he built in Hollywood and in our hearts, could be reaching its twilight. He is touched by our appreciation for all that he has come to mean to us. At that “Oh, Mary!” cast party, a stocky, ebullient woman approached and asked if she could show Spielberg the “Jaws” tattoo beautifying her calf. Of course she could. And even though Spielberg estimates that he has seen 30 of these since “Jaws” came out in 1975 (plus dozens of other tattoos inspired by his movies), he listened and marveled as though hers was his very first. Earlier, on the corner of 45th Street and Eighth Avenue, a young, fit guy with a blond ponytail sitting on a construction barrier looked up and said, with biblical concision, “Thank you.”