You know, you don’t need to take two and a half hours to do a funny, modern riff on Lina Wertmüller’s class-warfare-among-castaways classic “Swept Away (1974).” Even if you’re that Swedish slice of wry, Ruben Östlund.

But if cutting “Triangle of Sadness” means snipping off one second of a glorious, drunken mid-storm-at-sea debate about planned political economies between a tipsy Russian capitalist (Zaltko Buric) and a blitzed American Marxist (Woody Harrelson), well forget my pacing or excessive length complaints. Just pretend I never brought them up.

This mid-movie face-off, held aboard a small, exclusive and obscenely-expensive luxury cruise ship, begins with a Russian who made his money in “sh-t,” aka “aneeemal FERRRRtilizer,” quoting Margaret Thatcher and Ronald Reagan, and the ship’s American alcoholic captain firing back with Eugene V. Debs and Mark Twain.

“‘Never argue with an idiot,” the Captain says, quoting Twain. “They will drag you down to their level and beat you with experience.”

This tirade goes on, at length, as the Ship of Rich Fools is foundering in a storm, everyone on board too seasick to protest and the crew in total dereliction of duty — nobody’s on the bridge. And these two finish their debate locked in the cabin where the PA system to the ship is at their disposal and no crew member able to interrupt.

The director of the somewhat inscrutable “The Square” and the droll and dark “Force Majeure” (remade as “Downhill” with Julia Louis Dreyfuss and Will Ferrell) has filmed an amusingly heavy-handed smackdown of modern economic justice in a satire that, like “Swept Away,” is all about what happens when the social order is upended.

“While you’re swimming in abundance,” Captain Woody opines, “the rest of the world is drowning in misery.” That’s messed up. The rich folk, including the Russian “King of S–t,” are about to find out.

Our avatars in this comical riff on haves and have-nots are two beautiful people — together, it would seem, because of that one thing they have in common.

We meet British pretty boy Carl (Harrison Dickinson of “Trust” and “The King’s Man”) as he’s going through the shirtless and degrading audition for a fashion shoot, which a wag with a video crew sums up as “smiley brands,” aka cheaper products that sell you on the illusion of happiness that accompanies wearing them, vs. “grumpy brands,” in which the models must look sullen, aloof, too beautiful, expensive and unattainable, like the clothes they’re hawking.

The trick, one of the ad men says, is mastering control of “your triangle of sadness,” the space between your eyes and nose.

Carl reads and he thinks, which leads to quite a row with his model/influencer girlfriend Yaya (Charlbi Dean of “Don’t Sleep” and TV’s “Black Lightning”) over money, dinner, who’s picking up the check and “gender role stereotypes.”

But when they find themselves with a free trip on this luxury superyacht, with a wait staff of 15, a cleaning crew of five, armed security guards and a regular ship’s crew catering to maybe 25 guests, egalitarian Carl is the one who gets a crew member fired for almost flirting with Yaya.

Butch blonde Paula (Vicki Berlin) runs this operation and keeps everybody mindful of the crew’s job — “Say YES” to everything. But she hasn’t planned on the idle rich abusing that.

And nobody can get the damned captain out of his cabin for this one night-only “dinner with the captain” gourmet meal. He keeps drunkenly shouting them off through the door over the sounds of “The Internationale” on repeat on his stereo.

It’ll all come to tears, we just know it.

The passengers are a quirky collection of aged British arms dealers, rich men and their trophy women and the German couple whose wife (Iris Berben) has had a stroke. The only thing she can blurt out is “In den WOLKEN,” “in the clouds.” She shouts this a lot.

Östlund sets the clueless, entitled clowns up, and then knocks them down with one of the great seasickness vomit-offs in screen history. And as they exit the dining room and the ship rolls in the battered seas, the skipper and the amusing oligarch have their little good-natured drinking-game/debate.

Few of the characters are painted with anything resembling “broad, comic strokes,” and Östlund doesn’t fill in much background detail before the shipwreck, because we don’t know who’ll make it and who won’t.

That tends to undercut the “just desserts” nature of the satire. How can we relish the upending of the social norm if we can’t ID the most egregiously Musken/Bezos-ish of the entitled? Who among the working stiffs in the crew should we root for?

And how will this inform our beauty-is-fleeting model couple, who are just smart enough to know their earning window is closing and their relationship may have to find something else to lean on to survive?

I liked the whole first-season-of-TV’s “Survivor” turn things take, when the simple skills to survive are something no passenger in the lot has any clue about. Very “Swept Away.”

And I loved the long Woody and Zaltko (he was in “2012,” and the Danish “Pusher” trilogy of movies) face-off over the winner-take-all economy’s fascist tendencies.

The rest is entirely too obvious for its own good, something we’ve never been able to say about a Ruben Östlund before, and hopefully won’t ever say again.

Rating:  R for language and some sexual content, and that’s leaving out a scene of violence against an animal

Cast: Harrison Dickinson, Charlbi Dean, Vicki Berlin, Dolly De Leon, Alicia Eriksson, Iris Berben, Zaltko Buric and Woody Harrelson.

Credits: Scripted and directed by Ruben Östlund. A Neon release.

Running time: 2:27