The most fitting ending to the FoX-Men franchise is Dark Phoenix. A complete misunderstanding of beloved characters and stories, completely mismanaged by a movie studio that doesn't care about the franchise as a whole and has no intentions of managing the characters and stories in a way that would inspire continued success and loyalty among the fanbase. Just crapping out a movie with no regard for internal continuity or actually building to anything.
The Fox X-Men franchise died as it lived: being mostly bad and disappointing.