You are mixing separate problems. People still bought 20M copies, that's a success in itself. That said people buying 20M copies of a "broken" game is certainly a depressing trend - same with people supporting games riddled with microtransactions.
I'm a release-day player and I can honestly count the number of "annoying" bugs on one hand. However, I had a decent PC and the state of the game on last-gen consoles was ridiculous and unjustifiable. That said, the game was incredible.
robswc|3 years ago