If you like the main characters....

Hank, Magneto, Xavier, Mystique I think You will like this movie:

basically they decided to use the Dark Phoenix situation to create a situation for interpersonal conflict and character development

Perhaps they realized this would be the swan song for the franchise and thus focus on the characters as their send off. They already had committed to doing Dark Phoenix, so they had to do that story, just changed the emphasis

My prediction is that you will like this movie if you care about the characters less so if you don't

I really like the main characters thus I really liked this movie, despite all the flaws. It helps if you go in with low expectarions