It's not about forgetting. People don't just forget games that they connect with. Give players a game they connect with emotionally and they'll be stuck with you forever, regardless what shenanigans you do with it. That's what WoW did.
The problem is, like you said, the market is saturated and there are other MMOs that feel like the developers are putting in effort to develop and expand. I don't get that from SWTOR. The only reason I tried the game in beta was because it had the Star Wars tag slapped onto it, and the only reason I return once a year is to see, hope against hope, if there's any new content to try. Not much seems to change apart from such important matters like the loot crate animation.
There are options. People don't have to pay for this game when there are other more interesting titles on the market. Unfortunately, there's only one Star Wars MMO and so people need to subscribe to this one if they want some lighsabre action going. I'm fine with that but only for a short time each year to get my annual fix.