Grant Hodges’s review published on Letterboxd:
Holy shit, this movie sucks. No. You know what? You can't even call this a movie. The New Mutants is a bottle episode of a show you've never seen before... and never will again cause it was canceled after the single episode. I mean there are like six people and one set in the entire thing! Aside from the overuse of VFX (most of which don't even look that good), it's absolutely mind-boggling that this movie cost 80 million dollars. Like what was that money going to?
The plot is nonexistent, the characters are somehow even less developed (in a movie that should be ALL about characters), and the entire cast (which, again, is like six people) is giving career-worst performances - each of them apparently trying to one-up another in a "butcher an accent" competition. I will say I was legitimately surprised to see an LGBT+ romance portrayed so lovingly in a film of this size, so I will give it props for that. But otherwise, there is literally nothing to recommend. It's a dumpster fire.
A fun dumpster fire perhaps... but a dumpster fire all the same.