Didn't Diablo 3 suck? I quit playing that game after 2 weeks when it was released.
It was very very bad at release from the ultra-bland items to the content, story, and lore that basically felt like an insulting rush job after Act 1 (Act 4 was basically a series of white platforms suspended in air that they called Heaven). They eventually patched it up a few months later and it became passable - mainly because there were no other modern ARPGs yet - but it wasn't until the Reaper of Souls expansion that they gave it the true overhaul it needed. Unfortunately they have since gone overboard on some of the stuff and now the game is basically "play for a couple of hours, get handed a 6-piece set that does 1,000,000x damage...and that's your build."
The biggest crime is the sheer unrealized potential, honestly, but Blizz would rather do anything else than cultivate their coolest IP. There's plenty of game there for a newbie, but it's very stale for most others now. With Season 14 they're rolling out "themed seasons," and their big awesome idea? Double goblins. That's the amount of effort. Compare that with what GGG puts out for their ARPG every three months: