“Avengers: Endgame” does several things very well, among them achieving an enormously satisfying balance between humor, emotion, narrative clarity and action, and — as has been true with nearly every movie to emerge from this corner of the Marvel Cinematic Universe — leveraging the talents of superb, always-game actors to lend otherwise goofy material both mythic gravitas and welcome irreverence.

But perhaps the most important piece of fan service the movie provides isn’t a character wink or callback. It’s something that isn’t there. For the first time in an Avengers movie, there are no mid-credit extra scenes or final sting to hint what’s yet to come in the series. The beauty of “Endgame” lies in the fact that it’s really an ending.

Consider: In the decade-plus since “Iron Man” blasted the Avengers franchise into the cinematic stratosphere, millions of youngsters and teenagers have come of age never experiencing a film culture that doesn’t revolve around Robert Downey Jr.’s snarkily iconic character or Chris Evans’s stalwart Captain America or Scarlett Johansson’s cooly calculating Black Widow or Chris Hemsworth’s self-deprecating Thor or Mark Ruffalo’s soulful Hulk. For their forebears, the steady drumbeat of Avengers movies has been a warm bath of nostalgia, a reliable bet for their family entertainment dollar as they sought a reason to tear themselves away from their big-screen TVs. For their kids and grandkids, this isn’t just what movies looked like — this is what movies were. And part of that essential DNA was that, even if they stopped, they were never really finished. There was always another installment around the bend.

It might shock them to learn that it wasn’t always thus. Movie serials have been around since the era of “Flash Gordon” and “The Perils of Pauline,” of course. But some of us also remember a time when Bambi’s mother died, and stayed dead: That’s life. Butch and Sundance never made it out of Bolivia: End of. Even as formidable an archetype as the Godfather keeled over in his tomato garden and that was it: Basta.

And yet: “The Godfather” was too good — and too successful — to leave it at that. “Godfather II” managed to be both a prequel and a sequel, an early force in inviting audiences not just to like something and be grateful, but to say — yea, verily demand: More please. “Star Wars” changed the game for good five years later, ushering in the era of an ever-accelerating feedback between a corporatized Hollywood hooked on sure things aimed at presold audiences and viewers reluctant to stray beyond a lane narrowed by reassuring familiarity on one side and some-not-too-much novelty on the other.

Still, it bears remembering that fans of the first “Star Wars” movie had to wait three whole years until they were rewarded with a sequel, an exercise in delayed gratification that looks barbaric in retrospect. Even more than the Trekkers, Potterheads and Twihards who followed, Avengers fans were conditioned to expect not just more please but more right away, rarely going more than a year until their next fix. From the notion of cinema as a self-contained few hours of escapism, movies are now defined, not as discrete aesthetic events but component parts of a seamless, all-enveloping whole: We’re all watching One Big Movie now.

The glib explanation for the shift is that it’s all the logical result of baby boomers and Gen-Xers unwilling to grow up and incapable of letting go of their most cherished playthings. But it’s no surprise that the Avengers movies took hold at precisely the same time that the Internet and social media were changing audience behavior and expectations.

Suddenly, it was less important to be substantive than “sticky.” Engagement and immersion — which the movies had done best since their inception — became the coin of a realm. In a post-9/11 era of constant shock and cataclysm, we shouldn’t wonder that such novelistic plunges as “The Sopranos” and “The Wire” so thoroughly captivated their transfixed followers. When contemporary experience seems to be composed of narratively nonsensical shocks to the system, the attraction of coherent, well-constructed alternate realities cannot be underestimated. What better cure for our collective moan to “make it stop” than settling into a comforting fiction that promises never to stop?

With the “Avengers” saga and deepest-of-deep-dives “Game of Thrones” wrapping up this year, the defining poles of early 21st-century common culture are forcing their fans to grapple with ideas of closure, absence and interior loss that will probably leave their youngest fans feeling disoriented at best, disconsolate at worst. (“That movie messed me up,” a middle-schooler said at an “Endgame” screening this week.) We might have found that the best way to check out was to check all the way in, all the time, forever — but nothing is forever, as “Endgame” reminds us with elegiac solemnity and genuine emotion that are sure to ambush even the most skeptical fans.

Any movie based on comic book has the right — even the obligation — to play fast and loose with mortality, whether by way of supernatural powers, time travel or the quantum physics of brand extension. Just as the deaths in “Avengers: Infinity War” might not necessarily have been final final, so a slew of coming films and television shows promise to sustain our most beloved characters or resuscitate their fallen comrades. Admittedly, “Endgame” plays at the edges the indeterminacy fans have come to expect, but it’s not afraid to do something far more important. Eleven years, 22 films and innumerable characters later — with a few definitive finalities, at least one devastating, full-circle departure and no consoling end-credit caveats — it’s doing the difficult, necessary work of teaching a generation raised on never-ending stories how to say goodbye.