No. WoWs prime years were during Wotlk. WoW had the most subscriptions in that xpac. The pop dropped with the release of cata.
Your subjective opinion might be that TBC is the best xpac. I also like TBC the most. Nonetheless that's just a personal opinion and it doesn't represent the general consent.
https://i.kinja-img.com/gawker-media...5815773287.png
If it's really that simple then how does it come that Icecrown has now for over 3 years a steady 12k pop?
How does that go in line with your "people come and go" theory?