As I mentioned before, Marvel is a bit shy of adding mutants to the mix in Phase 4. They also have been claiming the whole diversity card, doing diversity all wrong because what you need to do is just add existing characters that are from different cultures races nationalities Etc... On what team could do diversity quite well??? I'm going to give you a hint:
Storm is from Africa Wolverine is from Canada Nightcrawler is from Germany Colossus is Russian we also have a Shopkins black we have Jubilee who's Asian so you get that whole diversity thing covered but you just do it not preach it to the winds... Because when you're praising yourself for diversity that probably means that you are not being diverse for real.
This is the part that some people are going to say:
But how do you explain mutants in MCU since they haven't been there?
Quite simple you just first state that mutants have existed for a long time but the KNOWN population has been quite small and not all mutants have noteworthy powers.
For example you have a mutant from say Wyoming who's great powers at he can see in the dark... or a mutant from Spain that glows in the dark. Or a Brazilian kid that has a second set of eyelids that allows him to see underwater and can swim rather fast but not breathe underwater.
Not every mutant has weather manipulation magnetism mind control or healing Factor.
So let's say until the New York incident of 2012 the amount of known mutants in the world where roughly about a hundred and 100 out of 7,128,176,935 (the nuber of people alive in 2012) is 1.40288325e-8 which is a very minuscule number. That's virtually 0% of the Earth's population. So in the comics the X-Men are known as the children of the atom, basically blaming the nuclear explosions in Japan as the event that triggered the next step in human evolution... or a massive boom on the mutant population I should say. Well how about we tweet that for the MCU saying that the incursions with aliens the infinity gems being used on Earth that Terrigen mists used within Agents of Shield and the Inhumans series, on the last but not least the infamous snap would be the triggers on the x-gene within the Earth's population.
That way you can have mutants that are already adults in the current ERA like say Storm, Wolverine, Magneto Sabretooth and have some younger mutants like say Scott, Jean, Hank, Bobby, Warren, Kurt, Etc.
And we could say like with the events of the 2012 incident in New York and the Avengers that maybe Xavier decided to try his school to avoid the potential for persecution and living in the post Snap era those who still are alive and are still normal humans would have some kind of grudge against super powered beings and we could have the whole Friends of Humanity hatred of mutants thing in the current year.
We could also tweak Bolivar Trask a little bit and having be a shield scientist that the Sentinel program began as a Defender against alien threats but due to 90s technology couldn't be made back then and basically Trask reviving his project in 2019 on his own after the rise of mutants and the whole snap incident.
The only big issue would be right now the whole Magneto being World War II victim, which would make him really old in 2019 finding a way to keep him Young is a bit more complicated.
A simple solution would be having Dame obtain something that can slow down the Raging for a little bit and remember that a while back I made on a video of how to add the X-Men into the MCU that he had the first movie being the original X-Men fighting Juggernaut and having a flashbacks of Xavier Magneto Cain Marko a tracker named Jimmy Logan tracking the temple of cyttorak... well maybe using that idea and giving them a blood transfusion from Logan would give them a bit of a healing Factor temporarily which would slow down there raging for a couple of decades just to have two 80 something men looking close to their prime.
The other would be making Antarctic equivalent of the heart shaped herb that slows down their aging.
La solution would be adding magic to the mixer the reality gem actual Magic I don't know something... It's Magic logic normally doesn't apply to it.
Wait savage land Nathaniel Essex mr. Sinister there we go mr. Sinister trapped them to experiment with them he prolonged their prime age due to the interesting Powers Within Magneto and Xavier... while it's no Shadow King this could be where Xavier would lose his legs.
And if they play it smart they could use the Disney plus Service as a way to prepare audiences with mini series setting up the future X-Men movies. I swear I mention Wolverine series Highlander crossed with The Fugitive I've have Logan roaming down the Northwest of the United States and parts of Canada as he's hiding from SHIELD and its Canadian counterpart. Then set up some villains like the Hellfire Club, Sabretooth, Omega Red, the reavers Silver Samurai, Etc.
Hell even a first-class miniseries which is basically about Xavier training the original five, told in flashbacks as he's explaining the facilities to the second class which would be composed of characters like Kitty Pryde, Nightcrawler, Colossus in a campus tour. I'm with the meeting series they got a lot of movie time in origin stories and all that.
Right now Disney has no excuse to not add the X-men... well, at least until 2021.