explanations of how Cap's time travel DOESN'T break the established rules... but honestly I don't really care either way. Time travel is always going to get weird. It's never going to completely make sense no matter how well done it is. I also thought the way they "ended" Cap's story was great. Really I thought all the original Avengers got some good closure although I think Black Widow got shafted a bit. I realize they didn't have a ton of time to mourn her when it happened but it would have been nice to see something more at the end when they were mourning Iron Man. I'm also curious how her death works in terms of the fact that there's supposed to be a stand alone Black Widow movie in the future. Obviously it could be an origin or story set in the past but that seems like a weird thing to do given that Endgame was kind of the end of the current phase of the Marvel Cinematic Universe.