They started charging for new heroes and made free cosmetics more difficult to obtain while adding other forms of monetization. Overwatch 1 was (somewhat) unique in that if you bought the game you had all the characters. I think this is these are the biggest reasons people are upset. There are other things like the lack of a promised co-op mode and a different format for matches but those are more subjective. It's hard to view Overwatch 2 as anything other than reworking the games monetization with little to no benefit for players. Calling it Overwatch 2 didn't help. It's Overwatch. It's not a new game. It's just a new version. The old version can't be played.