There was also this:
I forgot if them seeing Return of the Jedi was in the final movie or not (I think it was? Too lazy to check) but Jean's line "The third one is always the worst" was clearly meant to be a jab at The Last Stand but considering Apocalypse is the third one in the First Class era, all I'll say is....stones and glass houses.
But that was Apocalypse. Dark Phoenix? They didn't give a flying **** by that point that you couldn't tell it took place in 1992 at all. I think maybe Quicksilver wore a Nirvana shirt in it but that was it.