'You can't judge the game on the first 20 levels'. Yes you can. If it takes a casual player two weeks to get to 20 and in the process all they've done is "collect X", "walk to Y", "kill Z" using about 3 different class abilities then you can conclude that it is not a well-designed or fun game for the casual player. WoW is a hardcore game, for people that a) get to level 60, which by the way takes no skill and is no fun--just takes a lot of time--and b) have the time to raid a lot and get full epic gear when at level 60. At 60 you can enjoy beating new raid encounters, which is fun, although it stops being so fun when you're farming them every week for items, and PvP, which is not terribly well designed or balanced and depends a lot on gear.
The game is addictive, the game can be fun, but it's really not all that, and it's a completely crap game for a casual player.