Honestly, I hate the way some people speak of the X-Men brand as though they were just a disposable offshoot of Marvel.
No.
They are Marvel, just as Marvel as Spider-Man, Fantastic Four and Avengers. I do not think they should be jettisoned to a separate universe, because they're some of Marvel's most iconic characters and stories. Remember, the Avengers were considered a dumping ground to put characters who couldn't hold their own titles, and easily existed in the shadow of the X-Men. Few were clamoring for them to be more integrated until later, and whenever the X-Men and Avengers did team up, the Avengers were completely in the shadow of the X-Men. The fact is, the X-Men and all the worldbuilding they brought to the universe is very important to the lore as a whole.
Remember, the maligned Heroes Reborn reboot jettisoned the Avengers characters to their own universe to make them relevant (it didn't work), not the other way around.