Movie genres wax and wane over time in a way that can be borderline imperceptible. The Western did its slow fade through the 1960s, but it took a while to realize that it was heading into the sunset (and then, of course, it came back). On a less elevated level, I watched “Spa Weekend” and realized that the genre it’s in — the high-concept comedy with the concept in the title, the movie that puts out a vibe of “Look, I’m crass and dumb and obvious! And that’s why you like me!” — may now be entering its twilight zone.

Written and directed by Jon Lucas and Scott Moore, who made the brashly clever and likable “Bad Moms” (but were launched by their script for “The Hangover,” and in a way they’re still writing it), “Spa Weekend” is a comedy about four old friends who go on a deluxe spa getaway. The film has its minor-league version of a star cast (Leslie Mann, Anna Faris, Michelle Buteau, Isla Fisher), with Fisher cast against type as the Melissa McCarthy character — a foul-mouthed British trainwreck in insanely loud clothing who becomes the film’s bull in the aroma-therapy shop.

It’s all very standard, and the idea of putting the satirical screws to the New Age elitism of wellness culture certainly has potential. But watching “Spa Weekend,” you feel how tired and predictable the jokes are (it’s the script that needs a massage). And I’m talking about the “wild” jokes, like when the women take a raucous golf-cart ride through the spa grounds, or when a divorced couple work off their aggression by having a mud fight in a mud bath, or the moment when a session of “goat yoga” devolves — inevitably — into a Who let the goats out? free-for-all. It’s “anarchic” yet weirdly tame and expected. You watch these rote antics and think: Where are Barb and Star when you need them?

The four women are cardboard-cutout archetypes, played in amiable lightweight fashion. There’s Jane (Mann), a high-strung attorney and divorced single mother whose birthday weekend this is, and who is such an overscheduled control freak that she can only put a date with a man on her calendar three months in advance; Coco (Michelle Buteau), also divorced with two kids, who’s presented as a walking fount of anger issues (though if you call her on it, she’ll get angry at you for reducing her to the “angry Black woman”); Sophie (Anna Faris), a blonde mouse who’s been the personal assistant to a tyrannical boss for 10 years; and Fisher’s bawdy, antic, disheveled Mel, who the other three can’t stand, but as the movie explains — it becomes a central theme — every female friend group needs one person the others secretly hate.

I had mild hopes for “Spa Weekend” when it introduced the Solaris Eden Beach spa, a luxe white-on-white beachfront hotel that turns pampering into a form of exhibitionism. When Jane and her friends arrive at the front desk, they’re offered a choice of champagne or hibiscus water, and the spa’s general manager is a guru named Shanti (Erika Keynatz) who glows with well-tended superiority. Then, of course, there’s Kai (Adam Demos), the hot Aussie yoga instructor who makes instant eye contact with Jane (“C’mon, Magic Mike,” says Mel, “let’s see your big ding-dong!”). About 45 minutes in, Jane and Kai run into each at the otherwise empty hotel bar, and Jane explains that she can see right through the posh pretense of the spa treatments — the spaced-out music and yoga that’s just “stretching,” the Goopy optics of it all. But it’s as if the movie had already seen through its own joke.   

By all rights, Isla Fisher’s Mel should be the one making us laugh. I’ve always been a fan of this actor, and she gives a pinpoint performance as a dissolute narcissist who’s like a more unhinged Bridget Jones. But Fisher, in a weird way, gives too grounded a performance. She doesn’t have that spark plug of insanity in her DNA. (We don’t feel her unconscious need to destroy.) Or maybe the lines just aren’t crazy enough. Frankly, I had the same problem with “The Hangover,” a movie I always thought was more prechewed than it pretended to be. And you wish “Spa Weekend” found a way to give Leslie Mann, the film’s straight-arrow center of gravity, a bit more of a spin.     

“Spa Weekend” is being distributed by Black Bear Pictures — a good company, only this sort of thing used to be the province of major studios, and now it’s being relegated to the indie and streaming market. (See this month’s “Super Troopers 3.”) Nothing wrong with that, of course. But it’s a sign that overly processed bad-behavior comedies like “Spa Weekend” are a form that’s running out of gas. What happens at the spa stays at the spa. But it might as well not, since we’ve seen it before.