Women moviegoers, as we know, are egregiously underserved by Hollywood (the fact that half the human race is treated as a demo is an indication of how caveman corporate the thinking is). Yet if women are underserved, mothers are openly ignored. That’s part of what made last year’s “Bad Moms” such a broadly effective and well-tossed comic grenade. It was just enough of a foul-mouthed, let’s-get-trashed-at-the-supermarket party comedy that you might say it snuck into the “women behaving badly” genre.

Mostly, though, it was about something all too real and (in the movies) new: the high-maintenance, low-reward, whatever-you-do-you-can’t-win experience of middle-class motherhood in the age of the Mommy Wars. The movie took a few swipes at how underappreciated mothers are, but mostly it was about how guilty they feel for failing, in one way or another, to live up to their own stressed-out standards of maternal enlightenment. “Bad Moms” saluted and skewered its heroines at the same time. It was that rare thing, a crudely honest social comedy for the megaplex audience.

“A Bad Moms Christmas” brings back the same trio of sharp-witted stars (Mila Kunis, Kristen Bell, and Kathryn Hahn), the same raucously clever writer/director team (Jon Lucas and Scott Moore), the same infectious attitude of satirical sympathy toward the age of helicopter mothering. Yet the new film, while just okay enough to get by, takes a step back from the audacity of “Bad Moms” to something more cautiously conventional.

It opens with Amy (Kunis), now happily divorced and in a snug relationship with her perfect single-dad hunk, Jessie (Jay Hernandez), explaining in voice-over what a harried experience Christmas is for the moms who actually have to put the logistics of the whole season together. But her weary monologue is just a token link back to the first film. Amy, Kiki (Bell), and Carla (Hahn) head off to the mall, where they enjoy another slow-motion liquor-fueled free-for-all; this one features lap dancing with Santa and climaxes with the three stealing a Christmas tree out of Lady Foot Locker. Yet it all feels a good deal less outrageous than last time, since the trio have already seen the liberated light of delinquent motherhood.

They make a follow-up pact: This year, instead of busting their butts, they’re going to enjoy a relaxed, do-nothing holiday season, even if it means dropping most of the trimmings and ordering Chinese food for Christmas dinner. But that isn’t really enough to build a feature comedy around. What they need is more oppression to overthrow, and so “A Bad Moms Christmas” turns on the relationship between our heroines and their own smotheringly imperfect moms, who all show up the week before Christmas.

Each of these maternal harpies is a character out of an in-your-face sitcom, though Christine Baranski, putting a caustic spin on lines like “It’s December 19th — even the Jews have Christmas trees by now,” acts with such impeccable sourpuss bravura that she steals the movie. She plays Amy’s mother, Ruth, as a control-freak diva who barges into her daughter’s home like a cross between Carol Burnett and Federico Fellini. Ruth is obsessed with throwing the ultimate Christmas party (she’s already invited 184 people) and winning first prize in the local caroling cup. She puts up a series of holiday lawn decorations that look like a backdrop for the Rockettes. All of this clashes with Amy’s scaled-down plans, but the real problem is that Amy hasn’t figured out a way to stop taking orders from her mom.

Carla, as before, is the group’s slovenly wastrel, so it makes perfect high-concept movie sense that her mother, Isis (Susan Sarandon), is a reckless drifter in black cowgirl duds who gets dropped off by a trucker and immediately lights up a joint; she has no idea it’s Christmas, or even what year it is. Sarandon makes her a sweet-souled good-time petty outlaw, but you would never see this person anywhere but in the movies. Completing the circle of maternal narcissism is Kiki’s mom, Sandy (Cheryl Hines), who worships her daughter to the point of having no boundaries. She gets the same hairdo, sneaks into Kiki’s bedroom to watch her and her husband in the sack, and winds up buying the house next door. Hines plays her as a saintly kook, though when Kiki pushes back and Sandy starts talking about having “heart cancer, stage 12,” anyone who has ever been guilt-tripped by a hypochondriac mom will have a rueful chuckle of recognition.

The mother-daughter battles of “A Bad Moms Christmas” are lively in a cartoon way, yet they’re all-too-obvious variations on the overbearing-mom comedies of the last several decades, from “Terms of Endearment” to “Mermaids” to “Stepmom” to “Snatched.” Maybe the time is right for another one of these, but “Bad Moms,” in its farcical way, was an up-to-the-minute X-ray of attitudes. “A Bad Moms Christmas” sticks the Mommy Wars on the back shelf, and feels less distinctive — and hilarious — because of it.

The fearlessly inspired Kathryn Hahn once again plays Carla as a trashy suburban porno hellion who turns raunch into a second language. Carla now has a job giving Brazilian waxes at a spa, and the film’s comic high point arrives when she has to wax a male stripper named Ty, played by Justin Hartley from “This Is Us,” who makes him smart, goofy, romantic, and a dancer with moves to rival Magic Mike. The two strike up a flirtation in the form of a deadpan serious but insanely explicit exchange about the waxing of intimate male body parts, and the scene, in its way, becomes a satirical commentary on motherhood. When taking care of your children makes you feel like you’re suffocating, you might have to go this far to set yourself free.

“A Bad Moms Christmas” should appeal to the same — dare I say it? — demo that “Bad Moms” did, even though it’s not nearly as wild a comedy. It has one halfway original idea, which is that when you’re a mom yourself, the ability of your own mom to drive you nuts is heightened to the third power, because you’re competing on levels that are almost primal. Yet if there’s a third “Bad Moms” film, I hope it goes back to lampooning all the things that moms do to elevate — and subvert — themselves. “A Bad Moms Christmas” fills a niche, but as this series itself might say, moms deserve better.