"What is winning" in WoW is a very open question and doesn't 100% fit the "pay-2-win" model. Most of them have been stamped out but for a while there was a lot of mechanics in games where you could buy straight up buffs that meant you could perform better than someone who hadn't paid.
The reason I don't think this applies to WoW is there's nothing you can pay cash for that someone else couldn't get through playing the game. It might take a bit more work and time but you cant buy anything insurmountable.
But like you said the win conditions of WoW aren't necessarily just killing a boss or winning a battle. Once upon a time in a very similar thread I pointed out that for a mount collector WoW is very much pay-2-win because of the mounts they can only get by paying, and while this is mitigated by the token letting you exchange gold for Blizzard cash but I'm not sure how reasonable or practical it is to expect a player to get all the paid mounts that way.