To give the audience the sense of meeting the characters for the first time, in every movie.
From a 2014 interview with Simon Kinberg by Steve Weintraub for Collider on X-Men: Days of Future Past:
KINBERG: Yeah. One of the things, and this is an idea that came out of my work with Matthew Vaughn was, we didn’t want to do what most sequels do, which is ...
What we saw in Apocalypse wasn't the Phoenix Force.
It's not a retcon, because it's not said, in Apocalypse or Dark Phoenix, that this power we saw at the end of Apocalypse was the Phoenix Force.
Rather, it's a transition/climax scene of sorts which serves two purposes:
establish how powerful Jean is currently
plant the seeds for the upcoming Dark Phoenix ...
The Phoenix of legend is a bird that is born from the ashes of either itself or its parent. It has long been associated with resurrection and rebirth.
The Phoenix Force is so named (both in and out of universe) because it resurrected Jean Grey. It also usually manifests as a fiery bird.
This was what could be called a retcon
Reframing past events to serve a current plot need. The ideal retcon clarifies a question alluded to without adding excessive new questions. In its most basic form, this is any plot point that was not intended from the beginning. The most preferred use is where it contradicts nothing, even though it was changed later ...
Specifically regarding the meme, X-Men (2000) is not actually set in 2000, but in "the not too distant future". It could be another 30 years after X-Men: Dark Phoenix and in a different timeline anyway, where he didn't escape solitary confinement in 1973 and lived a less active and healthy lifestyle.
The only dating in the original trilogy is that Magneto ...