what if they made a movie about the justice league getting sucked into another universe that was like ours in the sense that the universe watched superhero movies and when they came they ran into a nerd who was trying to find out what universe they where from based on stuff like how many robins Batman had and there names and stuff like that
An addendum to your pitch: they arrive in our universe after trying to find the cause of a temporal anomaly that changed the events surrounding their confrontation with Steppenwolf. They eventually discover that the culprit is a gray CG Joss Whedon, and they spend the rest of the movie fighting to release the Snyder Cut.
They fail, of course, but they learn an important lesson along the way about accepting the immutability of the past and putting their efforts instead toward the future.