It’s a pity the great filmmakers can’t all bow out with “A Passage to India,” “The Dead” or “Charlie Wilson’s War.”

And it’s a shame Francis Ford Coppola didn’t have some dream literary adaptation, some piece of Italian or Italian-American history or grand vision he wanted to get on the screen — a master’s version of “Babylon” era Hollywood, his “Napoleon” or “I, Claudius” or “A Man for All Seasons.”

But here is the cinema’s greatest riverboat gambler, an Oscar-winning icon baring his soul and pouring his heart and money into one last roll of the dice, one last stab at relevence in the dying embers of a comic book movie age.

His vision of science fiction is “Megalopolis,” which is basically “Atlas Shrugged” meets “Caligula,” a civics lecture in “fable” form.

It’s about human creativity and a parable of utopianism and fascist oligarchy that overreaches even as it enfolds all the tricks of the trade that he’s learned in 60 years in cinema.

This self-consciously artsy, eye-popping extravaganza has a star-studded cast that includes a couple of Oscar winners and a few Coppola relatives. It has a screenplay that quotes the “To be or not to be” soliloquy from “Hamlet” at length, that references “Utopia” by Sir Thomas More and paraphrases Henry II’s invective “Will no one rid me of this turbulent priest” about Thomas Becket, and gives the line to Shia LaBeouf.

“Metropolis” reaches for parallels to our times, when “rich men,” rabble rousers and tech demagogues, are doing so much injury to human liberty and human potential.

But a barely coherent narrative underscores a simple fact. There is no getting around the heartbreaking truth that this is never more than a Messianic mess.

Adam Driver plays the John Galt/Howard Roark Ayn Randish “creative” figure. Cesar Catalina is a Robert Moses emperor of New Rome’s Design Authority, a man bent on remaking this mythical version of New York (the Chrysler Building is practically its own character) over with his new wonder building material, Megalon.

Coppola loves Japanese kaiju movies?

New Rome is roiled by economic disparity, and with one interelated family controlling the mayorship (Giancarlo Esposito), the most powerful bank (Jon Voight) and that design authority, in Cesar Catalina’s mind, it is is a place tailor-made for remaking.

He wants a city “people can dream about,” with soaring new buildings and people-friendly people movers, gardens for all and the like.

“Is this society, is this way of living the only one available to us?”

Mayor Cicero (Esposito) is an ex-prosecutor who thinks himself a man of the people, and he can only see the current unrest and all the ways “utopian” thinking fails to address genuine ills. He and Cesar have ugly history.

Catalina has an edge in the PR wars, as he’s sleeping with popular sexpot financial reporter Wow Platinum (Aubrey Plaza), aka “The Money Bunny.”

But the mayor’s gorgeous socialite daughter Julia (“Game of Thrones/Fast-Furious” saga alumnus Nathalie Emmanuel) is struck by this imperious, Nobel prize-winning, Shakespeare-quoting Lord of the Skyline, and stalks Cesar until he falls for her.

The hedonism is Fall of Rome/Weimar Berlin/NYC in the ’70s decadent, with clubs and parties for the beautiful people and street marches and riots for the have-nots.

Julia’s crazed, sometimes cross-dressing sibling Clodio (LaBeouf) figures he can tap into that undercurrent of unrest and topple this rival to his father, the mayor. Maybe his rich banker uncle Crassus (Voight) could bankroll that.

Clodio culturally-appropriates “Power to the people,” and he’s on his way.

Laurence Fishburne plays Cesar’s trusted aide and the fable’s stentorian narrator — “When does an empire die? When people no longer believe in it.”

Jason Schwartzman, nephew of Coppola, plays a mayoral aide and Schwartzman’s mother, Talia Shire (Coppola’s sister) plays Cesar Catalina’s mother.

The acting is pitched somewhere down the theatrically-grandiose scale, with only occasional snippets of dialogue meriting this approach.

Coppola brings in heaping helpings of effects, but found himself editing many great bits of eye candy into mere seconds of screen time in a tedious tale that runs over two hours, and feels much longer.

The madness of it all includes the look of the picture — swastikas and Roman SPQR signs, art deco and Cadillac Escalades. The design ranges from sleek, colorful and fashion-forward to the odd, jarring “What was that costumer THINKING?” This universe imagines “stop time” effects, magical floating moving sidewalks, classic Citroens, MGs and Bentleys sharing streets with Yukons and Caddy limos.

But the love story doesn’t click. Driver’s given many of the dumbest lines and most humbling stage directions and his struggle does nothing to dispel his “Box Office Poison” rep.

Plaza has the sexiest, showiest role, and she’s forgotten through most of the middle acts.

The muddle of characters merely clutter the narrative and the bigger point gets lost in a sea of small ones. Dustin Hoffman’s mayoral “fixer” figure is dispensed with as perfunctorily as this Great Threat hanging over them all, an old Soviet nuclear satellite that could hit Labrador, or doom New Rome.

But if you’re a film buff, feel free to ignore reviews, box office failure and everything else to see the last film by the screenwriter of “Patton” and the director of “The Godfather” trilogy and “Apocalypse Now.”

Coppola’s attempt to tap into a generation raised on sci-fi and comic book films fails. He can’t out-Gilliam Terry Gilliam (“Brazil”), has no patience for repeating himself (Helloooo, Ridley Scott) and has never been enamored of literary adaptations.

He’s been using phrases like “washed up” in interviews for nearly 20 years. I know. It’s why I buy his wine.

But if this mad gamble is indeed the “final film” of a great director from the Golden Age of great directors, cinephiles can celebrate the fact that at least he got it cast, filmed, edited and distributed and lived to see its release. That’s more than Orson Welles could say.

Rating: R, violence, sex, nudity, profanity

Cast: Adam Driver, Nathalie Emmanuel, Aubrey Plaza, Giancarlo Esposito, Laurence Fishburne, Shia LaBeouf, Jason Schwartzman, Talia Shire, Jon Voight and Dustin Hoffman

Credits: Scripted and directed by Francis Ford Coppola. An American Zoetrope/Lionsgate release.

Running time: 2:18