Read at your own risk:
I didn’t care for the ending but I do understand why the Russo’s likely went with the angle they did.
I’d rather have seen Cap do the snap and Tony live and retire with his daughter. That said, I think dying is the only way for Tony to quit. They had to make it final.
Regarding Cap: he went back in time and likely erased a relationship/marriage in order to be with Peggy Carter.
That said, I’m still undecided how I really feel about the movie. Kinda felt like time travel was a joke. Kinda like the Russo’s decided “Screw it, we’ll leave it for Scott Derrickson to figure out in Dr Strange 2”.