Isn't that what alternate universes are for? I mean, I actually think it would be cool to see an Elseworlds-type story that reimagines Professor X and Magneto as black men during the Civil Rights era, or better yet, an original story similar to that. Bob himself even pointed out Watchmen as an example of a story that was originally supposed to feature prominent DC superheroes being repurposed into an original work when talking about the people who wanted to remake The Last Jedi and encouraging them to do the same (come to think of it, the story I mentioned earlier could potentially be Marvel's answer to Watchmen). It's just that the people you mentioned don't have the talent to pull that off themselves, so they have to piggyback off other people's work.