What is holding back SWTOR the most?
The idea that a MMORPG, any MMORPG, must entertain and keep subscribers paying for several years or it is a massive failure.
This is the critical error that EA (and many other MMORPG publishers) as well as many MMORPG players make. In the pre-WoW days, there was very little competition so you tended to get hooked and stay in a game. When WoW came along it was the best of its class at the time. So it hooked people. And it created an explosion in MMORPGs. Many of those green-lighted in 2004-2005 came to fruition at a time when WoW had its playerbase locked into to their expansion strategy.
SWTOR is not a bad game. The elements that everyone whines about are elements people whine about in every single MMORPG. Guild Wars 2's forums are right now blown up with cries of lack of endgame, bad PvP, and the plethora of complaints that get lodged at all new MMORPGs.
Once you are resolved that these games don't need to become a long-term love affair, you'll be much happier.