That depends on what your actual goals are.
If you said, "I want to play WoW and have recreation time, and fuck everything else." then that could be true.
On the other hand, if you had goals for yourself that were impaired by the time or money spent on the game, and now you're wondering why you can't achieve those same goals, then you wasted your time.
You can play WoW in moderation and be fine. No question about it. And I am given to understand, it is much easier to be casual these days to boot.
However, if you look up many disorders, pathological behavior consists of actions done to such an extent or in such a manner as to interfere with the ability of someone to function normally in life, such as making a living, or even eating and sleeping properly. You certainly can play WoW too much, and you certainly can spend too much money on it, via paying for gold outside of the game.
If you're not measuring up to your own yardstick, you're wasting time, and not because someone else told you its wrong, but because you're objectively hurting yourself or preventing yourself from achieving your goals.
I used to be a guild and raid leader on endgame content. I remember more than one teen or college age student that was having problems and spent far too much time playing the game. Of course, I doubt the problem was solely the game, but they certainly used the time to do that, rather than addressing issues that they had.
As you'd expect, I used to play quite a bit myself, but eventually I realized that I simply didn't have enough time to play the game and still do what I wanted to do. It was time to quit. And looking back, I remember having a lot of fun. So, I don't regret it, but I also don't regret putting it down either.