All the universe's heroes giving up and trying to move on after years of trying to reverse the snap is a very impactful idea in theory. But the audience always knew they would get back together and reverse everything, it's why we're in the theater. So the impact falls flat.
It would've been interesting if they made all of phase 4 post-snap, and then the finale of that was Endgame. Then the audience could really feel the effects of the snap over years, and maybe also get that sense of despair and moving on, before finally coming back to reverse it. But that would be way too risky, and you definitely couldn't choose to kill Spiderman or any reasonably popular character in the snap.
_foolmo_
he says listen to my story this maybe are last chance