The timeline for X-Men is confusing at best, Futures Past was supposed to reset everything, yet Logan shows them in an entirely different situation, and never really explains how they got there
You can thank FOX for that. They mismanaged that property from the beginning. Aside from a few good casting choices, that entire film series was a mess.
I put together a chronological timeline of mutant movies and television series storylines, based on several sources, outlining how FOX used a shotgun approach with its X-Men property:
It is literally all over the place.
The animated series' popularity sparked the production of 2000's
X-Men, directed by Bryan Singer. I was against Singer and Simon Kinberg directing and writing, respectively,
X-Men: Days of Future Past. The movie was well-received but not by me. I was afraid an attempted reset, envisioned by Singer and Kinberg, would fall short. They diverted too far away from a CLASSIC storyline, overemphasized (again) Hugh Jackman's role, and overly focused on THE PAST instead of the extremely bleak future.
X: DOFP was a personal disappointing follow-up of my second favorite in the franchise,
X-Men: First Class. My number one favorite is
Logan but I do admit it does not strongly connect dots to what transpired beforehand. Of course, that was not the primary purpose of an Old Man Logan story. Its goal was putting a bow on one of Marvel's top characters, both inside and outside FOX's movies, while leaving an open-ended question mark of mutants' ultimate destiny.
All my hopes lie with Marvel and Disney oversight eventually making a clean mutant reset within its Marvel Cinematic Universe.
Doctor Strange and the Multiverse of Madness (very) loosely teased at what had transpired already under FOX's watch but I remain confident that was done solely as a fan service. The Children of the Atom deserve a fresh reincarnation. Then again,
Deadpool 3 may serve as a wild card for what may be coming, starting November of next year.
Timeline source links: 1, 2, 3