TLDR: It’s subjective, ill-defined, and the perception of a binary variable is overly simplistic.
Saying WoW is P2W is like saying black pepper is spicy. While true, in a world with ghost peppers and 5-million-scoville extracts, saying it’s spicy doesn’t convey a lot of information. Similarly, WoW’s P2W elements aren’t comparable to how P2W many other games are. Let’s first define some terms. There’s no universally accepted definition, but here is my definition that I think is broad enough to capture how most people think of the term.
Pay-to-Win (P2W): The degree to which an advantage can be bought monetarily.
The words “an advantage” and “winning” are interchangeable, however they aren’t well defined. Even if Blizzard removed tokens and only sold transmogs, a player who views collecting transmogs as “winning” will perceive the game as being P2W. The only scenario one could categorically say that WoW was not P2W would be if absolutely nothing could be purchased monetarily.
Assuming we agree on this definition of P2W, we can say that WoW is at minimum, a little P2W for at least someone. Personally, I view WoW as being very low on the P2W scale.
Why I view WoW as not very P2W:
My view is largely a result of what I consider “winning”. I see the capability to clear difficult content as winning. I don’t mean the ability to have already cleared difficult content. What I mean is that if you stuck a mediocre random player in a +25, no amount of money can be spent so that the mediocre player is able to compensate for their lack of skill. You can’t buy your way out of getting 1-shot and no amount of gear is going to compensate for a bad rotation. I’ve seen many players in dungeons who are essentially decked out in max gear doing 4-5K overall DPS while getting hit by everything. These people are outperformed by average players who are sometimes significantly less geared. Spending endless money is also going to do very little for an incompetent tank or healer.
If WoW were the only game with an in-game shop then it would universally be considered very P2W, but WoW doesn’t exist in a vacuum and there are plenty of games where you can effectively purchase enough power such that your grandparents could pick up the game and clear difficult content. That isn’t WoW.
The nature of how ‘power’ is purchased in WoW also matters. You can’t just immediately open up the shop and buy the most powerful items. You can be carried, but you have to wait for people not only to clear the content, but to be strong enough to carry you. When 9.2 drops you can’t buy your way to mythic raid gear immediately. Even when it’s available certain items aren’t guaranteed. There’s also an element of trust where you have to deal with a third party and feel comfortable enough to reveal at least some information to them. This alone deters many people from boosting. The existence of the boost is still a P2W element, but these differences are some reasons that I consider WoW not very P2W.
Once again, the degree to which you view WoW as P2W is informed by your personal definition of winning. There is a range to P2W and limiting it to “yes” or “no” overlooks a lot of nuance. In closing, however P2W you think WoW is, we should be cognizant that it’s in flux and remains only a single patch from becoming unambiguously P2W. It would only take strong items to be available in the AH for this change to occur. Because no new mechanics or systems need to be added, WoW could become heavily P2W in the blink of an eye.