There are many reasons why people might stop playing. No game lasts forever.
For starters, I don’t even understand the so-called problems – because I haven’t reached that part of the game yet. And while I was typing “not yet”, that’s not actually true – I don’t think I ever will.
I’ve looked at the Chaos Dungeons, and they are utterly boring with no rewards. Guardians and Abyssal Dungeons are multiplayer. Tower has unlocked yesterday, but I haven’t looked at it – however, I don’t expect it to be good.
I’m still doing the quests, but… since they took out the “progress” aspect by not giving you gear and levels anymore, they are also becoming really boring really fast.
Regardless of whether people can speed-upgrade their “T3” gear or not, or WTF the problem is that everyone complains about – I’ll be gone long before that even comes on the table.
Not everyone was starting the game looking for some MMO where they keep doing boring boss-rushes with cash-gear in self-proclaimed uber-player guilds for the next 25 years. People might just have tried out the game, played for a bit, and moved on.