10 Reasons X-Men Should Never Join The MCU
8. The Inevitable Recastings
If the X-Men were to join the MCU, it's pretty much guaranteed that all of the main characters would be recast, as they would have to establish a brand-new continuity. And while that may well work for some, there are certain actors in the X-Men universe that simply cannot or should not be replaced.
Absolutely no one is going to live up to the standard Sir Patrick Stewart and James McAvoy set for the role of Professor X, nor the one that Sir Ian McKellen and Michael Fassbender set for Magneto. Moreover, a recast of Wolverine is a near-certainty, seeing as how he's the series' most marketable character, but there is absolutely no way that anyone will be able to replace Hugh Jackman, which is exactly why the people at Fox are already hesitant to bring the character back themselves.
These actors are synonymous with their respective characters at this point and rightfully so, considering the time and effort they've put into portraying them. Fair's fair, Marvel has made some pretty brilliant casting decisions over the years, as well as effectively recast characters once owned by other studios.
However, this would be a lot more complicated than replacing, say, Ben Affleck as Daredevil, or Eric Bana as the Hulk. Nothing they do with the X-Men could ever be quite the same as what we've already gotten.