That's a nice thought, and on some level you're probably right, but there are a LOT of players that play WoW for the entirely different game it changed into and not only have zero interest in former design choices, but outright hate them. Fighting to get WoW back closer to its roots would be (and is) even more of an uphill battle than getting legacy servers is. A new server type is the only way to make both crowds happy. I don't think there's any way around that.
Separate, legitimate legacy/pristine servers also open the doors to direct comparisons which I personally feel as a great thing because it means that neither side can make grandiose, self-important, sweeping statements on the subject (like the classic, "it's just nostalgia!") unless facts support it (legacy servers turning to ghost towns after a few months). Right now it's a free for all where anybody can say anything because proof is impossible either way, and that drives me positively insane.