I think it's important that the plot not revolve around popular actors like it did with Jackman and Wolverine.
"The chief flaw of
X-Men: The Last Stand was that it told the “Dark Phoenix Saga” as a tragic romance between Jean Grey and Logan, two glorified strangers in the night. The actual co-star of the story, Cyclops, was unceremoniously killed off, Ice Man lost his big heroic speech, and the film stopped dead in its tracks so Wolverine could go to the “Fox Forest” and randomly kill a bunch of evil mutants. Now,
X-Men: Apocalypse stops dead in its tracks at the moment of maximum interest so that the young mutants can be shipped off to Akali Lake and can be rescued by a-cameo-ing Wolverine. Hugh Jackman’s Logan is an excellent character, and it’s something of a miracle that Jackman has played him this long (although I’d argue the time spread between
X-Men films which allowed Jackman to do other movies is a big part of that). The issue arises when the film pretzels itself, regarding story and structure, to justify Wolverine showing up to do his thing and/or take center stage."
I can see why they would choose to give a send-off or finish a series with the "First Class" crew. Though, I think that was rendered badly with so much going on.
X-Men needs a cohesive vision to sustain serialized storytelling, and going movie by movie just is not working. I understand that people like self-contained movies, but the thing is, the movies right now are kind of going in circles.