Judging Endgame by the standards of movies like 1917 or Citizen Kane seems silly. They’re so different in terms of audience and intent that they might as well be different mediums.
In my opinion, Endgame was a triumph of blockbuster comicbook storytelling that is unlikely to ever be equaled in film, but that doesn’t mean it is great in the same way that Casablanca or 12 Angry Men are great, nor should it try to be.