It's sub drops came from content droughts.

That wasn't what I saw. In my experience, the real damage that WoTLK did, came in the form of the Dungeon Finder. Blizzard forgot the fact that for many of us at least, the rewards of playing WoW were intrinsic; the fact that we enjoyed it and wanted to get as good at the game as possible. Look up the psychological studies on the motivational differences between intrinsic (improvement of skill) and extrinsic (gear and money, in WoW's terms) rewards if you want to understand what I'm talking about here.

The Dungeon Finder was built on the assumption that gold and loot were ends in themselves. So I'd do however many daily instances that offered X amount of gold, and then still be left hollow and trying to scratch the itch either with more farming, or with soloing old instances which still gave me an actual challenge.

The other problem with WoTLK, and the real reason why it was so popular, (and why, as other people have said, a vanilla re-release is not going to work) is because people want the ability to be bad at this game, and still progress through it. The Dungeon Finder was really a symptom rather than a cause of that, but the class structure of the Death Knight was a very clear example of it as well.

As a generation, Millennials are utterly devoid of anything remotely resembling integrity in the classical sense of the word. We (and I definitely include myself in this) would rather be on suicide watch due to the lack of accomplishment in our lives, rather than needing to actually earn something through discipline, commitment, and hard work. We are completely intolerant of any form of opposition whatsoever; yet we still want the same end result as if we had worked for it.