starstar-halfstar-outlinestar-outline(1.5 stars)

As movie theaters try to lure customers back, sometimes haltingly — with Regal Cinemas announcing the closure of its theaters less than two months after reopening — the trickle of theatrical releases has been a motley assortment, including Christopher Nolan’s not-quite-block­buster “Tenet,” Aaron Sorkin’s limited-release “The Trial of the Chicago 7” (a mere three weeks before coming to Netflix) and stuff like . . . “The War With Grandpa.”

This absolutely unessential — and only mildly amusing — family comedy tells the story of Peter (Oakes Fegley), a bullied 12-year old who begins feuding with his grandfather Ed (Robert De Niro) after Ed moves in with his daughter (Uma Thurman), necessitating the relocation of Peter’s bedroom to the attic. Alarmingly, the dingy space seems to have a bat and rodent problem.

In lieu of genuine high jinks, a series of escalating slapstick pranks ensues between Peter and Ed, including mishaps with a drone, a snake and a human corpse. None of them is especially amusing. (Think “Diary of a Wimpy Kid,” but with a more expensive cast.) Yet the narrative sets up an opportunity for Ed and his pals (Christopher Walken, Cheech Marin) to not just rectify Peter’s bullying problem, but for the two warring factions to somehow bridge the generational divide.

The comedy, such as it is, involves false teeth, underpants and, somewhat distressingly, not one but two scenes in which Ed accidentally loses his pants, inadvertently flashing Peter’s henpecked father (Rob Riggle). The characters, who also include Peter’s two sisters — one a faintly adorable moppet (Poppy Gagnon), the other a bratty teen (Laura Marano) — are all pretty standard issue for this sort of thing. Thurman is especially wasted in a personality-less role that could have been played by anyone. Only Walken, with his signature daffy charm set to simmer, seems to be having much fun.

The movie, sadly, continues De Niro’s drift, over the years, from prestige drama into poorly reviewed comedy. Based on a book by children’s author Robert Kimmel Smith, “The War With Grandpa” takes obvious sides here, aiming squarely at the demographic of school-age kids with nothing better to do while insulting the memory of “Raging Bull” and “Goodfellas” — along with anyone old enough to recall them.

PG. At area theaters. Contains rude humor, strong language and some mature thematic elements. 94 minutes.