This time, Vardalos’s Toula Portokalos and her extended family must deal with the death of the family patriarch, played by Michael Constantine. (Constantine appeared in the first two films and died in 2021. Mom, played by Lainie Kazan, isn’t doing so well herself, failing to recognize her own daughter in an early scene.) But never mind. Toula, along with her husband (John Corbett), her brother (Louis Mandylor) and her Aunt Voula (Andrea Martin), among others, are headed to Greece for a family reunion. The trip also gives Toula the chance to fulfill one of her father’s last wishes: to present his childhood diary to a long-lost old friend.

Forget that the pages of this supposedly decades-old journal look as fresh as something plucked off the stationery shelf at Target. Time is fluid in this cinematic world, and the series chronology follows suit: At the end of movie No. 2, Toula’s daughter (Elena Kampouris) was off to college. But here — apparently seven years later — she confesses that she’s just flunked out of her freshman year. Time has taken its toll on the faces of nearly every other character.

Continuity quibbles aside, the threadbare narrative essentially turns into a “Roots”-y travelogue. Toula and company land in their ancestral village to be met by the enthusiastic guide (Melina Kotselou) who has organized the reunion festivities. Of course, there’s a catch: When the six members of the Portokalos family arrive, expecting a huge gathering, they discover that they’re the only relatives who have shown up.

There are other twists, including long-lost family members, wild goose chases and a pair of young lovers who provide the eponymous third wedding. In contrast to the sprawling threads that sent the second film off on detours that didn’t pay off, this time it’s the entire thin plot that doesn’t pay off.

For a 91-minute movie, the Portokalos clan certainly spends an awful lot of time in transit. Recurring shots of the same winding road soon start to resemble the work of David DeCoteau, a filmmaker who built a cottage industry of straight-to-video films based in part on heavily padded, threadbare plots filled with footage of winding roads so repetitive it becomes surreal.

And yet there are themes here (and throughout the Greek Wedding films) that should resonate with anyone from an immigrant family — anyone from a family, period: culture clashes, the difficulty of assimilation, tension between tradition and modernity. But the situations are so cliché, the conflicts so glossed over, that the connection gets lost. It’s not for nothing that there’s a recurring gag about Windex.

If the 2002 film addressed these issues in the form of a cute extended sitcom, its sequel raised the characters’ cartoonishness to cringeworthy levels. In a scene from the 2016 film, Toula yells at her neighbors for making fun of her family, no doubt prompting more than this reviewer to want to shout: “But you’ve spent the whole movie depicting your family as obnoxious buffoons!”

Thankfully, such buffoonery is toned down here. But we’re still left with cute but thinly drawn characters with little personality beyond signature quirks, like the penchant of Toula’s brother for grooming himself at the dinner table. At least he’s a recurring figure; the new young lovers introduced in this film have little to distinguish them, other than their amorousness and their non-Greek heritage. (The young woman is a Syrian refugee: an attempt at timeliness that feels tacked on.)

Even Martin, whose character provided some of the most pleasurable moments in the other films, isn’t given much to do. One longs for another lurid tale from her of the parasitic twin she mentions — so unforgettably — in the first film. Why not give that lost twin their own plot and a wedding in the next sequel? The mind reels. On a more serious note, a parasitic twin is a brilliant if gruesome metaphor for unmet potential: the thoughtful work of art about the immigrant experience lurking inside a fluffy piece of undercooked entertainment.

For all its faults, “My Big Fat Greek Wedding 3” manages to just get by on pretty scenery and a meticulous inoffensiveness. What else is there to say but, “Opa!”

PG-13. At area theaters. Contains suggestive material, some nudity and extended broad stereotypes. 91 minutes.