When it comes to the nostalgia effect and how people's recollection of things have changed on a consensus level, I think WotLK is actually the starkest example of just how changeable the vox populi can be. In its heyday, I remember WotLK as being almost universally derided and criticized, both in the community spaces and in-game as well. There was the sense that the overall change to the combat flow (sped up and made much more ARPG than the Classic/TBC model) "ruined the game." There was of course the whole controversy and hate-fest around the ubiquitous GearScore add-on gating who was eligible to do what content. There was the addition of the Dungeon Finder LFG system, which was another addition players complained incessantly about. The TotC raid was received pretty poorly after much more epic Ulduar. Even the addition of Achievements to WoW was viewed by some as a "dumbing-down" of the game.
Fast-forward to today and WotLK is remembered mostly as WoW's Golden Age and its watershed moment, a high point at which WoW's popularity began to roll backward through successive but never quite as remarkable peaks and valleys. I have one guildmate who was deeply cynical and scornful about WotLK while it was current, but when I recently asked what they thought was WoW's point of greatest popularity, waxed on nostalgically about WotLK and how great it was.