6) The (Un-)Altered Timeline
Days of Future Past changed things for X-Men in much the same way J.J. Abrams’ Star Trek reboot shifted things for that franchise: the film virtually rendered all the movies that had come before moot, wiping the slate clean so Bryan Singer and co. could start over. This has allowed the director to take the characters in new directions, but he also now has a problem: the timeline of the world as we know it should be altered, too. Only, in Apocalypse, it isn’t.
The end of Days of Future Past found Richard Nixon almost assassinated and mutants making their presence felt for the very first time. Major events, which would have changed the world. However, by Apocalypse, everything has shifted back into place: Ronald Reagan is president, Return of the Jedi is out in cinemas, Eurythmics are on the radio, and everything is exactly as it was in the real-world 1983. It’s as though Days of Future Past never even happened.