Set during a reunion for boomers, writer-director Castille Landon’s comedy also stars Eugene Levy and Dennis Haysbert.

If Hollywood aims to bring older audiences back to theaters by making movies about them, I submit Summer Camp as a case study in what works (Eugene Levy!) and what definitely does not — painfully flat attempts at wackiness being the chief offender. Veering between strained slapstick and thoughtful tête-à-têtes, this boomer-focused reunion comedy strands a game cast of accomplished septuagenarians in a mostly laugh-free zone of zip lines and predictable beats.

A backstory sequence reveals how the trio of misfit Pinnacle campers became inseparable in their youth. Keaton’s studious Nora (Taylor Madeline Hand), Woodard’s gentle Mary (Audrianna Lico) and Bates’ slightly older and more worldly Ginny (Kensington Tallman) had one another’s backs, especially when it came to withstanding the taunts of Pinnacle’s standard-issue mean girls, known as the Pretty Committee, and played in their present-day incarnations by Beverly D’Angelo, Victoria Rowell and Maria Howell.

The problem is that everyone here is quite clearly one thing, and that thing needs fixing. Keaton’s widowed executive is a workaholic, Woodard’s married emergency-room nurse is chronically selfless and put-upon, and Bates’ Ginny has turned her take-charge worldliness into a self-help empire with more than an edge of know-it-all bossiness, with a catchphrase, “Get Your Shit Together,” that’s clearly destined to boomerang on her.

Bates and Woodard can each pack a world of nuance into a gesture or glance, while Keaton’s dithery routine, as showcased here, feels calcified into distracting shtick. It’s hard to believe that hemming-and-hawing Nora is a CEO. On the other hand, the moments of vulnerability that break through her fluster have that much more impact for disrupting the pattern.

A best-selling author with a shoutily branded tour bus, Ginny strong-arms Mary and Nora, who haven’t had time for a get-together in years, to join her at Camp Pinnacle’s weeklong reunion, its very first, and surprises them with a glamping-caliber bunkhouse (the low-key production design is by Scott Daniel).

Both Nora’s tween crush, the “whip-smart” Stevie D (Levy), and Mary’s, the “handsome as hell” Tommy (Dennis Haysbert, who’s the youngster in the central cast, turning 70 a few days after the movie’s release), show up at the gathering, conveniently single and gently rekindling those long-ago flames.

Haysbert hasn’t much to do here except offer the mellifluous depths of his voice and exude good-guy vibes, which he does exceedingly well. A scene that might be the comic high point belongs to him and Woodard: a nearly wordless sequence at a pottery wheel, the intimacy and the giddiness — not to mention the phallic symbolism — well captured by cinematographer Karsten Gopinath.

Levy’s retired exec counters Nora’s compulsive devotion to her job with his relatively newfound commitment to work-life balance. More than that, the very pace and modulation of his line readings bring the movie’s sputtering, choppy energy to a compelling place of quiet.