As someone who plays both D3 and PoE, my only gripe with D3 is that there is no 'finish line' (like e.g. level 100 or 40/40 Challenges in PoE). Every time a D3 season starts, I just have to ask myself "if I'm not going to play for the whole ~3 months, why even bother?"
I wish that at least your "highest rank on the leaderboard achieved" in Diablo 3 saved somewhere on the profile. I mean, sure, the people who farmed the whole season deserve their credit and high ranking finishers and a place in the hall of fame, that's fine, but I think that my rank 1 achieved mid season should have some weight too. It being visible to people who specifically inspect my profile would be ok.
It just feels pointless to do that again, and I don't want to farm the whole season either, which just means I do the season journey and quit immediately. And the season journey is just remarkably short, and the only way D3 endgame is actually fun is if you push. It just feels like a terrible design loophole.