Apart from it being cringe it seems to be rated pretty highly on imdb and rottentomatoes, is it well acted etc? Is it intentionally cringe?
Let's be honest alot of stuff in bodybuilding has been cringey for a long time, there's that scene in pumping iron where the black guy hits his crab shot moving his arms about and a guy in the audience is stamping his feet and screaming

I thought the acting was mid. Jonathan Majors is a well regarded actor but I thought he waaay overplayed the part. He didn't come across as a fan of bodybuilding, or even a fanatic but more like someone with aspbergers.
Midway through the film loses direction. Starts of sbout a guy who has dreams of being a pro bodybuilder and getting on the cover of muscle and fitness. Then it turns into something more about him being an incel then about mental illness and anger issues.
Majors imo wasn't "acting" the part of a bodybuilder. It was more like poorly pretending. And there's a difference between acting and pretending. Though he was more believable in the anger sequences of the movie.
Lastly, it was a character study of a wholly unlikeable person. At first you want him to do well but by the 3/4 part of the movie he's a character that you don't like or care about. His elderly father, who's only a bit part in the movie is a far more compelling character, imo. Ultimately it was so depressing I didn't finish watching it, again much like a royalty post.