I played the game probably way longer than I should have, Steam records over 1000 hours which doesn't even include the time when I wasn't playing on Steam.
It started out pretty good for me. Early levels aren't too bad, and a lot of the dungeon mechanics are actually very interesting and fun.
By the time I stopped playing, game development had been going in an increasingly bad direction. Things were becoming increasingly and ridiculously grindy. I suppose in some recognition that it was too grindy, they implemented a bot system that would control your character in a limited fashion that helps with some of the more mundane grinding.
At some point, even with sinking ridiculous hours into the game, it's nearly impossible to be competitive without cash shop purchases. Dungeons start to become gear-gated. Many of what were once challenging dungeon mechanics become trivial once you hit a gear threshold. And you end up running these dungeons a ton of times because of how grindy the game is, and it really becomes a chore.
Both in PvP and PvE, class balance doesn't seem to be handled very well, which becomes increasingly clear the farther you progress. This may have been fixed in the meantime, but was one of the main reasons (along with client instability and the absurd amount of grinding) that I stopped playing. I was playing one of the two classes that were considered basically unviable in PvP (Protector and Marksman).
On the plus side, I've heard good things about large scale PvP and inter-server PvP have been added as well, but it's not enough to make me come back to what I feel is a broken game.