I've seen a few people claim that there is "general consensus" that WoW Classic is actually a WoW period that includes Vanilla, TBC and WotLK. Is it though?
TBC and Wrath introduced 2 of the worst features of WoW: flying mounts and LFG tool. That's where, arguably, "the decline" started.
All of a sudden claiming that Classic period is a thing is a bit disingenuous.