What works best about Christopher Markus and Stephen McFeely’s script for “Endgame” is that one feels, for arguably the first time, a sense of looking back instead of merely trying to set the table for something to come. This film incorporates elements of what fans know and love about the MCU, recalling character beats, origins, and the plots of movies like “Iron Man,” “Guardians of the Galaxy,” and “Captain America: The First Avenger.” Call it cheap fan service, but one of my biggest issues with these films, especially “Infinity War,” has been a sense that they’re merely commercials for movies yet to be made. “Endgame” doesn’t have that. Sure, the MCU will go on, but this movie has a finality and depth given to it by MCU history that the others have lacked.