The X-Men franchise has used the concept of time to its advantage over the course of the last few years, but now the timeline has become nearly untenable.
A reboot would allow the X-Men franchise to consolidate its characters into a more cohesive and coherent timeline, which in turn would allow for easier crossovers.
The primary X-Men team is currently stuck in the 1980s (soon to be 1990s), Deadpool is currently enjoying himself in the present day, and Logan, X-23, and Patrick Stewart’s Charles Xavier are stuck in the future.
The problem is that so many vital characters have become scattered across several different time periods.