I think Kromtor hit the nail on the head. Lemme asplain (All thoughts are my own personal experiences):

When I logged into EQ to play I rarely had an agenda other than to have fun. The goal of the game was so loosely defined. Ultimately, of course, I wanted to be max level--But I had no game plan to get there. Sometimes I'd read some forum saying I should go explore this place and try out this spot or maybe go farm this mob for this item etc etc. Doing *anything* in the game was an odyssey. I remember farming up Wu's Trance Sticks and the ridiculous amount of time it took to get them. I remember farming Raster in LGuk for weeks. I remember trying to find 50+ people to do the raid bosses for my Epic. Looking back on all of these things one immutable thing stands out: They were each an adventure that I felt damn proud of for completing. They each took dedication and energy and friends.

WoW is nothing like that for me. Everything is just plain so easy to do. The two arguably hardest things to do in the game (achieve Gladiator status or complete all the raid hardmodes) actually come down to finding a group of other people that are as dedicated as you are. If you can find 2 other people that complement your class well and are willing to play 3-4 hours a day at the same time as you you can get Gladiator. With raiding you just increase that number to 9.