I'm not concerned about the 90's setting that's the most awesome thing I like about the movie and apparently the post credits scene(two of them btw) were dope so it has to be something meaningful.The vast majority of the movie takes place in the 90's breh. I'm not saying don't go see it but (and I haven't read spoilers) I doubt it ties into "Endgame" in any kind of meaningful way. Unless there's something in the post-credit scenes.
Fred.