People complain but the content of WoW, FF14, Eso, etc ... is incomparable to SWTOR.
Idealism of the fans?
Bioware and EA themselves sold the dream with their articles and commercials before the release of the game.
If a lot of people are gone it's also because this game was clearly far from over when it was released.
If SWTOR had come out with more than class story, players would have stayed and could have done the other activities. The devs clearly underestimated the speed and difficulty that the other activities would have had. Most activities were done in 1-2 days after the release and the rest of the time had to do what? Add to that the stuff of operations and flashpoints that were worth nothing compared to the stuff of leveling, no wonder everyone gets stuck if when you encourage a player to do an activity, there is no carrot at the end.