I think the main thing that affects people these days is S-E's extremely poor customer service.

With that said, there are still plenty of people playing. I believe FFXI is ranked the 4th top MMO and has a combined population of Everquest 2 and Lord of the Rings Online -- I think it was around 700k-1M. Although there are some servers that don't have as many players, and the population used to be a lot larger.

In any case, the game ain't dying.