Okay - So during this movie I felt what most people have; confused, annoyed, and even more confused. What I've found in my searches is that due to the events in Xmen Apocalypse some timey-whimey (aka someone messed with the time lines) stuff occured. Which means that this Dark Pheonix/Jean(Gene?) as well as EVERYONE ELSE is not the same as those characters from the Xmen movies that started this off back in the early 2000's. I could be wrong..but that was what most sites are saying - honestly just google it if you care enough.
I myself really enjoy these newer Xmen movies, perhaps even more than the the original Hugh Jackman led ones. But I think this one missed the mark in a lot of places - especially since the director/producers are making a movie within a series thats within another series. Where's the pre-movie recap of current events when you need it, eh?