It gets a bad reputation here because it isn't a dungeon crawler RPG anymore like the previous PSO and PSU entries. It is... something else.
It's more of a standard MMO formula now, with constant planned obsolescence and the vast majority of relevant content being time-gated, and having 90% of the game be "dead content" since the game deliberately designs itself to have all players doing the same thing.
It's not necessarily a bad game, but it just isn't PSO anymore. It tried to be when it first released, but once Episode 2 came in 2013, it went a completely different direction and has been doing so constantly. I honestly believe it has a case of no identity, because they keep throwing things at it and hoping they'll stick.