Those look like potentially flight/space suits.
Granted, the X-suits have pretty always been flight suits, so...
I can barely make out the details, so hardly worth judging based on that picture. Definitely could be a lot worse. We've had films where they don't wear costumes, and lots of black armor.
They're wearing blue and yellow with giant X's, and they're wearing uniforms. That's a win in my book.
There has to be a reason for the uniform look after the varied costumes at the end of APOCALYPSE. It almost looks like they're "marketing" themselves as the X-Men with their outfits. That's pretty cool.