Noah Baumbach’s eighth film as a writer/director opens with some pointed onscreen quotes from Henrik Ibsen’s The Master Builder, establishing the animosity those in middle age exhibit toward the younger generation. The fact that Ibsen’s observations were first published in 1892 only underlines that the conceit of While We’re Young has long been—and will always be—raging.

Cut to a newborn’s face as documentary filmmaker Josh (Ben Stiller, star of Baumbach’s acerbic 2010 film Greenberg) and his wife/producer Cornelia (Naomi Watts) demonstrate their lack of parenting skills by freely using the word “fuck,” fumbling with the baby as a music-box rendition of David Bowie’s “Golden Years” plays on the soundtrack. Ah, but this baby isn’t theirs. A childless couple in their mid-40s, they’re visiting their best friends, new parents Fletcher (Adam Horovitz, aka “Ad-Rock,” erstwhile member of the Beastie Boys) and Marina (Maria Dizzia). But they’re soon relegated to supporting roles as Josh and Cordelia open their door to a young hipster couple, nascent documentarian Jamie (Adam Driver, from Baumbach’s last film, 2012’s Frances Ha) and ice cream maker Darby (Amanda Seyfried), who crash Josh’s continuing-education class.

Josh, who’s spent nearly a decade working on a film that he’s nevertheless unable to describe, is thrilled that someone is showing an interest in his obscure work. Soon, he’s taking up an invitation to visit Jamie and Darby’s bohemian loft with Cornelia, despite her initial protests.

“We don’t even see our real friends—why do you want to spend time with a couple of 25-year-olds?” she asks. But once Cornelia unwittingly joins flagging best friend Marina at a mommy’s group, she finds herself child-deep in the movie’s biggest moment of sheer, hyperventilating horror. Fleeing the guitar-led sing-along, Cornelia meets up with Darby, who brings her to a “hip-hop class”—a sequence that taps into Watts’ underutilized inner comedian as she awkwardly flails about, more uncoordinated than the babies she just escaped.

Meanwhile, Stiller thankfully underplays his typically outsized comic persona as Josh takes Jamie under his wing. Re-energized, he begins to act more and more like his young protege, affectedly wearing a thin-rimmed hat and riding a bike—and painfully peddling his way toward a diagnosis of arthritic knees.

While Josh and Cornelia enjoy their flirtation with youthful reminders of a more hopeful past, Baumbach employs a montage that cross-cuts the couple indulging in their modern electronic conveniences—iPhones, iPads, cable TV—while Jamie and Darby stick with discoveries from an earlier time, such as paper, typewriters (electric, but still) and vinyl records.

Marveling at the thousands of albums lining the walls of Jamie and Darby’s apartment, Josh notes, “This is just like my record collection…except mine are CDs.”

Subtly humorous, naturalistic lines like that are what lift Baumbach’s best pictures past many of his contemporaries’. It’s when he gets bogged down in plot machinations that his movies can sometimes suffer—and there’s a surfeit of plot here compared to, say, Frances Ha, in which Greta Gerwig dashes through Manhattan as Bowie’s “Modern Love” backs her sprint and lifts your spirits.

Spirits aren’t just lifted in While We’re Young; they’re also violently expelled. Drifting further away from their aging Generation X contemporaries, Josh and Cornelia turn down a cookout invitation in order to join their new millennial friends at a weekend-long ayahuasca ceremony.  “Puke out your demons,” says the hippie shaman (Baumbach regular Dean Wareham of the band Luna), who tries just a bit too hard to set a New Age mood by playing Vangelis’ “Love Theme from Blade Runner” from his iPod as buckets overflow with vomit.

Soon after, Jamie strikes upon an idea for a documentary of his own. Josh finds the concept thin, but he’s flattered by Jamie’s offer to have him co-direct. “This generation is so generous!” he proclaims, even after he’s just picked up Jamie’s lunch tab. Again.

Later, feelings get hurt when Josh and Cornelia drop in unannounced on their old friends, only to discover a large party filled with 40-somethings that they weren’t invited to. “You’re an old man with a hat,” Fletcher tells Josh, whose ego takes more hits in a problematic third act as Cornelia’s father, Leslie (a white-haired Charles Grodin, rounding out an impeccable cast), an elder statesman of the documentary scene’s cinema verite era, offers to look at Josh’s sprawling work-in-progress.

Duplicities pile up, as do resentments, but this film—and Josh—aren’t Greenberg. The honesty can still be bitter at times, but there’s a newfound sweetness that’s crept into Baumbach’s last two pictures. With the passage of time comes the realization that the cruelty of life doesn’t have to sting so hard when tempered with the love of a partner. That, and a good bottle of Scotch to share.

While We’re Young ***

Starring Ben Stiller, Naomi Watts, Adam Driver, Amanda Seyfried, Maria Dizzia, Adam Horovitz, Peter Yarrow, Dean Wareham, Brady Corbet and Charles Grodin. Written and directed by Noah Baumbach. At Boston Common, Coolidge Corner and Kendall Square.