I've loved the X-Men movies. X-2 is still better than Logan to me. It's all people's opinions, honestly to me none of them have been fantastic game changing movies, but I really enjoyed Dark Phoenix way more than I anticipated. It had a lot of comic book mutant action, which is what I want from a comic book movie. I don't care too much about being close to source mateiral. We're 40+ years at this point from a lot of the "classic" X-Men stories.
The other thing is whatever will be introduced in the MCU will not be anything like the comic X-Men. I can't imagine anything will be similar to the civil rights issues of the original comic series. Being a decade+ into the MCU, whatever they introduce will basically be an afterthought, or at worst shoehorned in. For instance, you're not going to get an 80+ year old Wolverine who may have fought in WW1. You're not going to get an Apocalypse who's 5000 years old. Retro-actively introducing all that now in the MCU would seem super stupid to me. Like wtf were these guys doing for the last 10-15 years then?
Plus if you're talking popularity, you can't deny a lot of the movies did well and IMO Hugh Jackman is right behind RDJ and Chris Evans in terms of Star+comic character person. Jackman may even be above Evans to some.
I really think the appearance of x men is going to be something strongly based on the ultimate universe comics.
In fact, there are several things that the MCU can copy the comics for, for example, answering some questions that you raised:
Wolverine may be a hundred years old, in fact he appears in "the first Avenger" movie without credits or they can make him a Vietnam War veteran (a Rambo-like character).
Magneto may also appear during the second world war, as it is one of the guinea pigs of the super soldier serum.
Apocalypse could be linked to the Eternals, explaining his absence during the years of the MCU's history.
The very question of the absence of x-men or mutants in general could be something related to memory erasure or even the x-men (the first class) started in the 90s, something went wrong and they disappear in the next 20 years.
Cyclops in the 90s would be 15, 20 years later he would be only 35 (ideal age for a team leader). The first team can be something like magneto, xavier, mystique, cyclops, storm, beast and some older characters to appear as mentor figures of younger characters, like ice man, Kitty, colossus in the MCU present.
