I'm going to try to explain WoWs appeal in the context of gaming at the time.
I started playing MMO's with Everquest around the release of Velious. For those gamers of the master race, that was what PC gaming was all about. Waiting 30 minutes to catch a 30 minute boat ride across an ocean was awe inspiring. Blowing yourself up at the forge trying to make a worthless item was orgasmic. Running around Antonica for better part of half an hour having to use different disguises and spells to run the Stein of Moggok quest was gleeful. This wasn't a game, it was a fantasy
simulation. And you got to play with other people who enjoyed this crazy stuff just like you.
Of course one bad decision, a spell ending early, getting in a group with with an average IQ below 70, or just using the forge could very quickly make hours, days, weeks of grinding go down the tubes.
What attracted the master race to this game, also created burn out. But the social aspect of the game was what made it addictive. You suffered through the horror and reveled in the achievements with friends and enemies, making new ones along the way. But only those in the niche of the most masochistic pc gamers.
Steady continuous income from a game was appealing, and a lot of companies thought they could improve on EQs formula to either get a different niche (pvp) or create a better ui to attract a larger chunk of players. I was able to get my girlfriend at the time to play DAOC with me on occasion and enjoy it, and she wasn't a pc gamer in any sense of the word.
Blizzard got the formula right. Some how the mix of cartoony 3d graphics, large open world, instanced dungeons, arena pvp, just enough danger and difficulty to make people feel like they've achieved something, animated emotes, and not to forget the floating (!) all resonated with a huge audience. Not only did gamers want to play, but people who weren't even gamers by any stretch of the word were also subbing in droves.
My girlfriend had seen quite a few of my LAN parties, after this game released she started organizing her own. She used trial accounts to let her friends come over and play the game. I had 3 pcs that could run the game, some brought their own. Here was a bunch of young women who thought video games and Nintendo were synonyms, and who didn't know the difference between a USB or Ethernet jack having LAN parties to play a MMO. And they were subbing and continuing to play on their own!
But, for the masochists, it was watered down tripe. For the not so extreme masochist, it was fun until they got bored or until they personally felt Blizzard jumped the shark. For all the others it was a way to socialize until a change of life event took them out or enough of their friends left that it wasn't fun anymore. I have no idea who the people who play the game now are. My guess mostly new blood who having gotten bored yet.