I consider TBC as the greatest thing ever since I was hardcore raiding through it, just because I played through it a 2nd time after 2.4 on a new account(moved from US to EU server), just made it easier, not better.
But I can see TBC was a horrible experience as well if you didn't have contacts or a guild to go through all the attunements, because Tier 4-5-6 was deeply locked away for a long time until 2.4. As well as Resist gear checks still existed, crafted with expensive or raid-exclusive materials.
(2.3 and Zul'aman gear/badges did help a bit, but still wouldn't be anywhere near Hyjal/Black Temple level of gear)
Wotlk wasn't the worst thing, as things like same-realm raids and dungeons existed, and had an end boss many wanted to finally see.
In hindsight it was a hybrid of TBC/Classic design going forward, albeit also continuing on more catch-up mechanics and vendor gear.
It also was an experiment as well on new game concepts like 10/25 raids, hard modes, and heroic modes all shown in different tiers.
I liked 10 man raiding in Cataclysm/MoP a lot more again as it didn't feel like an inferior difficulty, and you also were locked to only 1 raid clear a week again instead of 2-4 in wotlk.