I was excited to see some new mutants (get it?) come to the big screen, but this is definitely a Young Adult movie, first and foremost. The whole film feels muted, with no big plot points, no shocking reveals, and no twists to keep you wondering what's going to happen. They set up this spooky old "hospital" as the setting, and barely do anything with it. All of the scares that take place in this "horror movie" are just mildly creepy visuals, like it's a Goosebumps book.
So why 2 stars? Why not 1? Because it feels like they tried to do the source material justice, at least in terms of the characters. Maisie Williams' Rahne is probably as close to Wolfsbane in the comics as it's going to get, Scottish accent and all. Sam and 'Berto don't have the full buddy dynamic down, but still work well together, and look great when they (finally) use their powers. Majik, however, takes the visuals to 11 with her limbo-hopping, sword-wielding antics, and is definitely the highlight of the movie. Moonstar is...there.
Basically, the third act shows that these characters have potential, especially if merged into the MCU with other X-Men, but you have to sit through a dull movie first.