Maybe the definition of madness is “doing the same thing over and over again, expecting a different result.” That doesn’t really explain Netflix’s mania for big budget/”name” cast disaster movies.

“Don’t Look Up” was merely the most-hyped. “Bird Box” had Sandra Bullock. Remember “Extinction?” Their shot at Dom DeLillo’s “White Noise?”

Yeah, I’m leaving a few out. But Netflix must be tapping into a pretty good-sized audience for this genre. Because while there are differences between their many efforts in such films, one thing they invariably share in common is that they’re all…lacking.

“Leave the World Behind” stars Oscar winners Julia Roberts and Mahershala Ali, along with Ethan Hawke and a nice Netflix supporting actor check for Kevin Bacon to cash.

It’s got a few bromides about “We need to get along before we’re torn apart” politics, a couple of “gotcha” moments that almost deliver, and the most amusingly pointed shot ever taken at Tesla in a mainstream film.

But there isn’t much to it, and you can feel it going wrong right at the start as veteran TV producer/show-runner and sometime director Sam Esmail (“Mr. Robot,” “Homecoming”) indulges too much in little musical montages, showing off either his taste in R & B, hip hop, etc. or his movie’s music rights clearance budget. Early and often, we’re treated to Next, Joey Bada$$, Blackstreet and TV on the Radio tunes underscoring a light moment, or set to choreography for a dance scene.

Sure. OK. Quit stalling. Get to the story you want to tell, whydoncha?

Roberts plays Amanda, a tetchy, tense ad agency rep who impulsively books a weekend for herself, college prof husband Clay (Hawke) and their two teens Rose (Farrah McKenzie) and Archie (Charles Evans).

They’ve got to get out of New York, out to a “hamlet” on Long Island. Because Amanda’s come to a conclusion about herself.

“I f—–g hate people.”

They pile into their Grand Cherokee and make their way to a McMansion in Point Comfort. But the strident strings and nervous piano in the score warn us something’s up before they notice.

It happens on the beach.

“Look at that boat. It’s so big!” “It’s getting closer.” “I think that ship is headed towards us.”

A huge tanker runs aground right in front of them. “Nav system issues” they’re told.

Then the wi-fi, TV, radio and phones go silent, and just when 13 year-old Rose was getting close to the end of her first-ever “Friends” binge.

Well after dark, there’s a knock at the door, and two Black strangers hem and haw through how this is their house that they’ve rented and would they mind awfully much if they stayed here for the night, as there’s a blackout in the city and nobody knows anything about what’s going on.

The best exchanges come here, with a tuxedoed Ali as the owner (he says) who never actually talked to the renters by phone, who conveniently lacks ID and whose 20something daughter (Myha’la) isn’t taking Amanda’s borderline racist mistrust and wariness of these two without sarcasm.

“It is, you know, OUR hourse!”

It takes a while to ask for that ID. The fact that George, “G.H.” (Ali) has keys to the liquor cabinet and cash to reimburse them for the inconvenience is enough for the “reasonable” Clay. But Amanda is seething.

And their “tests” are just beginning. More or less, anyway. Because something bad is going down.

Planes will tumble from the sky and all the region’s Teslas will migrate “home” as a drone drops red leaflets in Arabic and flashes of phone service and TV “emergency alerts” sketch in little except that something terrible is happening.

Darkness in mid-day, deer gathering in herds to stare at the house, ominous shots from space that show us satellites and even a moon’s eye view of the imperiled Earth, ginning up a little suspense about what and where the “real” menace may be.

Kevin Bacon is well-cast as the grinning survivalist who figures the fact that he’s been prepping makes him all-knowing about their situation.

Roberts is on-brand as the ill-tempered shrew in all of this, and Hawke similarly is typecast as Mr. Reasonable but an academic ill-prepared to keep his family together and alive.

Ali does what he can with a character who seems to have lots of answers or suspicions of answers, meaning that he’s got to be the omniscient deliverer of exposition and screenplay “shortcuts” to answers. Or more questions.

I’d say the suspense is killing me, but it never came close.

“Leave the World Behind” is not awful or wrong-headed or particularly insightful as a parable. It just isn’t very good at what disaster movies are supposed to be good at. Aside from making stuff crash and burn (even those scenes lack much in the way of punch), what does this tale tell us about human folly and the State of America?

And yet, Netflix persists in making films like this because, like “Friends” reruns, people can’t stop themselves from watching them.

Rating: R, violence, lots of profanity

Cast: Julia Roberts, Mahershala Ali, Ethan Hawke, Myha’la and Kevin Bacon.

Credits: Scripted and directed by Sam Esmail. A Netflix release.

Running time: 2:13