7/10
I suspect some of this film's failure comes from high expectations, and the unnecessary pressure of the movie having to be the "Swan song" of the franchise. There's also the inevitable comparison to Disney's Marvel Cinematic Universe, which is such a high bar. Personally, I enjoyed "Dark Phoenix". Because of all the negative drama surrounding the production, and the fact that the movie can be seen as a rehash of X-Men 3, I went in with low expectations. That was a good thing, because in comparison to other films in the franchise, I rank it pretty high.
Dark Phoenix is small in scope, and repeats the mistakes of it's predecessor Last Stand - taking an epic saga that spanned years to tell in the comics, and reducing it to one film. When I heard that Dark Phoenix was going to be just one movie, I knew the film was destined to fail. The previous films - First Class, Days of Future Past and Apocolypse - work as a trilogy. Dark Phoenix arguably should have been part of a second trilogy, which could've dealt with the rise of the titular character (Phoenix Rising), the fall (Dark Phoenix) and the aftermath (Phoenix Resurrected). But 20th Century Fox was never good at dealing with X-Men on an epic scale. Perhaps they knew that doors were closing, and that they couldn't do that many films.
Despite its small scope, this film is more faithful to the source material than Last Stand, and seeing Jean Grey in a central role was delicious. Xavier's character arc is painful, and has a palatable resolution. Magneto too plays a hefty role, providing the counter-balance to Charles. Though some characters had little to play with, the cast's chemistry works, and what we do get to see as far as team work and powers is satisfactory for the scope.The main villains are rather generic and slightly underdeveloped, not being the actual aliens from the comics. But there's enough there for motive and backstory when it comes to the villain-of-the day formula.
Dark Phoenix is not the best X-Men film, and it's not the worst. It's comfortably in the middle. Go in expecting a fun superhero movie ride. Don't go expecting Avengers-level spectacle, and don't go wanting a big send-off goodbye. These are not the intentions of the film.