Audiences are showing fatigue when it comes to Marvel’s box office behemoths of recent years. Based on what they were served in 2023, it’s hard to blame them.

Iman Vellani, Brie Larson and Teyonah Parris in “The Marvels.”Credit…Laura Radford/Disney/Marvel Studios, via Associated Press

At the center of 2023’s “The Marvels” is Carol Danvers, a.k.a. Captain Marvel, who, if you’ll recall from the 2019 film “Captain Marvel,” destroyed the all-powerful A.I. leading the Kree empire. Joining Carol Danvers is Monica Rambeau, a.k.a. Photon a.k.a. Pulsar a.k.a. Spectrum, who was first introduced in “Captain Marvel,” then later featured in the Disney+ series “WandaVision,” where she was granted superpowers after an encounter with reality-altering witches. And joining these two Marvels is the teenage New Jersey native Kamala Khan, a.k.a. the titular character of the Disney+ series “Ms. Marvel.”

That’s a lot to take in, which is why the first few minutes of “The Marvels” is just a series of flashbacks designed to catch the audience up before the action even begins. Even for dedicated fans of the Marvel Cinematic Universe, the amount of prerequisite knowledge required to watch any M.C.U. movie or show nowadays is tantamount to a college course.

And it seems like audiences are tiring of the constant homework assignments. A year of diminishing box office returns is more proof that the casual superhero moviegoer is becoming more and more of a rarity given how much is being asked of them, which is full, multiplatform investment.

These franchises are spelling their own downfalls, as the price of entry into the fandoms has become frustratingly high for the dedicated disciples of these worlds, and not at all worth it for casual viewers or prospective new fans. This year has been a prime example of what happens when a pop-culture movement takes hold of an industry and then overreaches. We’re witnessing Ragnarok.

The barrage of offerings and the uniform, assembly-line quality of the plot structures make it easy to forget that the M.C.U. used to excel at providing entryways for those too intimidated or simply not enticed by the grand Avengers throughline. In the series’ Phase One, “Captain America: The First Avenger” jumped to the past for a World War II period piece and “Thor” offered a mystical world of Norse gods. “Guardians of the Galaxy” ventured out even further, to a universe larger than what was happening in Avengers central, with its own funky soundtrack, and “Ant-Man” fittingly zoomed in to a more playful, humbler superhero story. These films not only allowed prospective fans more opportunities to step into the mythology but also added texture to the franchise, diversifying the tones and genres of the films so every new one didn’t feel redundant or strangled into a larger plot.

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Opening weekends became cultural watershed moments, with the box office numbers to back them up. A-list stars, thrilling action sequences — summers were defined by the superhero blockbuster, with audiences glued to their seats through the M.C.U.’s signature mid- and post-credits scenes, as the films insisted on holding fans at attention until the very last word. The 2010s were defined by the likes of “Black Panther,” “Guardians” and the “Avengers” movies, which for the most part were warmly received by critics and enthusiastically devoured by fans.

But Marvel’s narrative fatigue has been building for a while now; in fact, I wrote about this creeping danger as “Avengers: Endgame” and its three-hour runtime landed in theaters. But it isn’t just the storytelling structure that’s been hurting; it’s that middle “c” in the acronym, the cinematic element, that has also declined.

“Guardians of the Galaxy Vol. 3” was the highest grossing superhero movie of the year. Credit…Marvel Studios/Disney

Consider the latest batch of superhero offerings: Of this year’s films, “Guardians of the Galaxy Vol. 3” made the most money, but was dour, off-putting and didn’t offer the closure that the trilogy had seemed to move toward; this sequel was ultimately meant to serve as a changing of the guard, introducing a new lineup of Guardians. “Ant-Man and the Wasp: Quantumania” was widely panned, and for good reason; it got tangled up in its psychedelic pseudoscience with no payoff but a mishmash of poorly executed visual effects. On the DC Comics side, the most impressive feat “The Flash” managed was casting a problematic lead actor as not one but two versions of the same character in a tedious time-travel plot that had already been pulled off more successfully in the TV series of the same name.

And though “The Marvels” was set up to be the big superhero blockbuster of the fall, it was a rote example of the form — unimaginative, unremarkable and purely targeted to audiences already in the know. It has performed miserably since its November release, with Disney president Bob Iger (who oversees Marvel Studios) taking the rare step of publicly admitting the movie’s shortcomings. It’s the worst-performing M.C.U. film so far, and a perfect representation of the exhaustion on both the creative side and audience side.

Back when these superheroes were still on print pages and not big and little screens, Stan Lee, the godfather of American comics and the creator of many of these characters, used to include what he called “Bullpen Bulletins” in his issues. These informal letters to readers, including announcements, promotions and context for and commentary on his work, were indicative of Lee’s relationship to the fandom. He fostered a community around his heroes, built from the ground up: He maintained a dialogue with fans, treating them as not mindless consumers but highbrow connoisseurs of the art form.

Whatever “Bullpen Bulletin” factor may have ever existed with today’s superhero consumers seems to be fading fast. As franchises — particularly the M.C.U., fueled by Disney’s multibillion-dollar appetite — continue to grow and threaten ever more, ever greater crossovers, it’s becoming more difficult to understand what their endgame is (pun intended) when it comes to their fans. Who wants to watch 30 films and 10 TV series to engage with a franchise that continues to spread itself too thin at the expense of quality filmmaking?

Nostalgia alert: Michael Keaton dons the Batman suit once again, with Ezra Miller in “The Flash.”Credit…Warner Bros. Pictures

That will be left only to the completionists, who have invested this much time and effort and will see these stories through to the end, and to the fans held hostage by their own nostalgia. There’s a reason the latest go-to cinematic gimmick is callbacks to decades-old incarnations of heroes: the trifecta of Spider-Men in “Spider-Man: No Way Home” and the alternate Batmen from “The Flash.”

These cameos don’t serve the ambivalent 10-year-old who never saw Sam Raimi’s Spider-Man movies or Michael Keaton’s Batman. Neither do the several minutes of catch-up flashbacks explaining all the story lines leading into a new movie.

The franchises continue to risk fatiguing their current fans and alienating potential ones. More stand-alone films, more inventiveness, more diversions from the grand plots and cookie-cutter setups would give these stories and their fans room to explore, but instead we’re stuck in a cycle of ever-expanding multiverses, narratives and timelines that even the best S.H.I.E.L.D. agents would find impossible to keep straight.

The ultimate irony? These commercial superhero machines know exactly how their approaches can be self-sabotage … because they keep offering stories in which their heroes fall into the same trap. The antagonist of “The Marvels” opens rifts that tear through space and time, introducing other realities that can collide and destroy everything. In “The Flash,” Barry Allen (the hero’s alter ego) has to explain to an alternate version of himself that they can’t keep manipulating the time stream. “These worlds,” Barry says, looking at the C.G.I. representations of space and time around him, “they’re colliding and collapsing.” “We did this,” he continues. “We’re destroying the fabric of everything.”

Superhero movies changed the industry. No matter what you think about them as art, the upswing of these comic book stories from the margins to the drivers of popular culture was swift and remarkable. But now these Clark Kents and Bruce Waynes and Rocket Raccoons and various Marvels risk orchestrating the end of this Age of Heroes.

But like in every superhero movie, there’s hope yet: Stories that end. Characters who die. Universes where the stakes are real and cameos and meta-commentaries aren’t just crutches to bait audiences. Stories that don’t cling to a crumbling concept but perhaps start fresh in another corner of the universe.

Superhero movies used to be super. The heroes are still as strong as before. They just need the movies to match.