Anybody who’s debating whether to attend his high-school reunion will certainly be dissuaded from doing so by watching a few minutes of this dismal dramedy about one. The characters fashioned by writer-director Jaime Linden in “10 Years” are such an insipid, irritating bunch that spending time with them will hardly encourage you to choose to revisit your old classmates.

The ensemble assembled for the movie is large but mostly undistinguished. Notable among the 28-year olds returning for the event are Jake (Channing Tatum), who brings along his girlfriend Jess (Jenna Dewan-Tatum, the actor’s real-life wife), to whom he’s planning to propose. But he might just see his old high school flame Mary (Rosario Dawson) at the bash. Jake and Jess drive to the suburban home of his pal, buffoonish Cully (Chris Pratt), who’s got three kids with his long-suffering wife Sam (Ari Graynor). Also showing up at Cully’s place are successful singer-songwriter Reeves (Oscar Isaac), Scott (Scott Porter), who’s now living in Japan, and two comic-relief types, New York yuppie Marty (Justin Long) and his chum A.J. (Max Minghella), who’s married but on his own. A.J. looks to act as “wing man” for his bachelor buddy, especially if the once-upon-a-time campus hottie Anna (Lynn Collins) shows up. And Reeves looks forward to seeing wallflower Elise (Kate Mara), a mousy type that he always had a secret thing for.

Everybody shows up, of course, Anna alone and still sultry, Elise twice divorced, and Mary with husband Paul (Ron Livingston) in tow. And there are a raft of others, including Garrity (Brian Geraghty), whose wife Olivia (Aubrey Plaza) is discomfited to learn that her hubby was a white rapper (or “whigger,” as she calls him) and his old friend Andre (Anthony Mackie), whose fast-talk at least prods some of the verbose scenes, marked mostly by longing looks and shy smiles, along.

This is a motley crew, whose personal problems (mostly revealed in the final reel, staged largely at a local watering hole that was once their teen hangout) are of the most obvious sort, and whose badinage is unfortunately natural in being the sort of lame, puerile put-downs and idiotically meaningful remarks that empty-headed twenty-somethings are prone to say. Whether most of it was actually penned by Linden or improvised by the actors doesn’t matter; it’s dreary and mirthless in any case.

All the performers have fared much better elsewhere. But one has to feel particular sympathy for Pratt, whose character wants to use the event to apologize to all of the outcasts he was a “dick” to a decade earlier, but gets smashed and winds up harassing and insulting them all over again while Sam looks on, and Aaron Yoo, who plays Peter, the main object of his incompetent regrets. Running a close second are Minghella, who’s positively creepy in his attention to both Marty and Anna, and Long, who’s supposed to be charming but is far from it.

To add to the insult, the picture is visually unattractive, with Steven Fierberg’s camerawork making the locale look shabby and Jake Pushinsky’s editing coming across as lackadaisical. But he was probably hard-pressed to find acceptable footage for a full feature in the alternately silly and treacle-filled stuff that Linden dumped on him.

“10 Years” makes one long for the halcyon days of “The Breakfast Club.” Compared to a homecoming with these dolts, teen detention seems like paradise.