It’s hard to know whether to welcome “X-Men: Apocalypse” with melancholic disappointment or testy annoyance.

Bryan Singer, a more than capable director, once again returns to the Marvel mutant saga he began in 2000. He launched the first two films in the series with a level of craftsmanship and intelligence that turned the comic-book genre into big, serious business. Without those game-changing hits, Christopher Nolan’s dark Batman trilogy and Disney’s witty, irreverent Marvel Cinematic Universe might not have arrived.

And now there’s this hollow, unfocused mess. Singer’s fourth X-Men film is not just a step down, it’s a fall down the stairs.

This time the story is action all the way. There are a dozen sequences where the camera tumbles down some rabbit hole of doom, or looks on while immense boulders crush casualties. They feel like visual diagrams of the movie’s collapse. It’s big in scope and scale and tiny in originality. Using the new term “drop” for a movie’s release was invented for tailspin declines like this.

The X-Men films have bounced across various timelines, springing from the Holocaust to Hiroshima to the 1970s to the recent past as if the superpowered characters were on trampolines. This episode deposits them in the ’80s, but opens with a dismal prologue in Egypt, 3600 B.C. Flattening landmarks is an action film staple, and here the destruction hits a gargantuan pyramid. Inside that structure is En Sabah Nur aka Apocalypse (Oscar Isaac, unrecognizable in steely blue makeup), a ruthless entity absorbing eternal life through ornate enchanted technology.

His immortality is halted when guards betray the “false god,” crashing the sloping walls atop him like dominoes. Millennia later he returns to the surface like a really cross mummy, raising an army of evil mutant allies and making magic-wavy-hand gestures against humans.

Apocalypse also seems to be juggling the film’s convoluted plot lines and character back stories, which scarcely fit together. A large cast of 16 comic book characters returns here, eight of them recast since their last appearance, none of them holding center stage.

James McAvoy’s schoolmaster for young mutants, Professor X, delivers another serving of his signature charm, moving into new, anguished territory only when Apocalypse grows to Paul Bunyan size and pounds him with giant fists. Michael Fassbender reprises his role as the antihero Magneto, levitating himself while pinching his face into a constipated scowl. Jennifer Lawrence as the chameleon Raven/Mystique propels her scenes through sheer force of personality. Her dialogue and character arc are so creatively malnourished that Scarlett Johansson’s walk-by role as Black Widow in “Captain America: Civil War” pushes her aside in its wake.

Hugh Jackman’s speechless cameo as Wolverine works; 16 years since he created the role, he’s still a remarkable roughneck. But his minor presence here is sheer fan service.

The bedrock virtues of Singer’s earlier work, from “The Usual Suspects” and “Apt Pupil” through his superhero crowd-pleasers, were his commitment to surprising and challenging audiences. His characters had unexpected dimensions, and his stories had a meaning or two that he would not allow to fall out of focus.

Never for a moment does this X-Men revisit the issues of tribal prejudice, minority rights and alienation that made his earlier films so compelling. Here we have a team of characters in high-tech battle gear combating a rival squad of bad guys as Dr. Evil aims to wipe out our world for no clearly defined purpose.

Even die-hard Comic-Con fans can take only so much of this, but the film’s attention to international marketing seems likely to deliver a hit. Olivia Munn’s villainess Psylocke swings a samurai sword that should delight fans in Asia, where 70 percent of film profits are mined today. The film would be a success if the only thing that mattered about producing movies was making a profit.