There were short examples of non-insular collaborations that created great excitement but flopped due to abyssmal stories. One was Freddy v Jason. Another was Alien v Predator.
Universes are really cool ideas because it takes skill to tie in these different elements into ancoherent story, but that’s my gripe... I don’t think we’re getting good story. I think we get flash and bang and a passable serving of story.
But then again it is just a kids movies. But then again...is that an excuse?