There, I said it. Hang me up high til my neck stretches too far. I don't like Icecrown Citadel.
I'm not going to waste time trying to define fun or interesting since you'd say it's wrong anyway. But the first wing is not fun, except gunship, which is easy but at least different. Festerface and Rotgut aren't much fun either. Putricide is almost fun, definitely fun as the abomination, though also quite simple and easy.
Heal dragon fight is not fun either. Run here and kill this then runthere and kill that and nothing lasts more than a few seconds. It just feels frantic without being truly difficult. Sindragosa is a bit of fun, but frost breath irritates me as a tank.
Blood council is boring as a tank or melee. But as a nuclei catcher I've had fun. Blood queen is boring. Biting is a fun idea, but in practice is just a source of stress, or in 25 a call for addons and I'm no fan of fights that demand addons or even do more than slightly encourage their use. This is part of why I hate healing.
But at least there's Arthas. Except I don't enjoy that fight either. Phase one is boring. Phase 1.5 is boring. Phase 2 is some combination of irritating RNG and excessively precise positioning. Phase 3 is boring. It's fucking irritating staring at a release button for half the fight duration while Arthas and Tirion have a shouting match. A free last 10% doesn't feel fun, it just feels like I'm doing PvP with a rogue around.
I didn't feel any sense of accomplishment, pride, joy, or even relief when I got my first kill. I just thought "oh, I ran out of health". That's no way to feel after killing the last boss of the expansion. And I'll stick with the Insane, thanks.
I cannot blame all of this on ICC. More than a little bit, I believe, comes from having spent months longer wiping in ICC than I should have. I associate it too much with needless wipes, not from mistakes, which happen, but from players just plain not trying, not listening, not grasping basic concepts of fights or even roles. So when bosses died, it did not feel like my accomplishment or our accomplishment, but simply the eventual outcome of for once someone by accident not uttterly and completely failing.
And tanking in general has been pretty much straight downhill this expansion, with only a brief period of fun and challenge back before we overheated everything. Ret DPS wasn't much better, with T10 being a lovely source of lag-based DPS loss.
While I'm at it...
Naxxramas was a giant pile of crap.
Malygos was too soon and three dimensional vehicle fights do not fit in WoW, not the audience, not the game engine.
Ulduar was fairly fun but felt like it got cut off too much from the Storm Peaks setup due to having a raid and too much tome in between, not that I'm blaming blizzard for the delay, it just didn't work well for the immersion factor.
ToC was too hyped for being basically ICC-lite. Not much fun and somehow too short to be substantial but long enough to feel like I wasted a night.
I forgot Sartharion. 3D is brilliant for nothing else than showing exactly how ridiculous gear inflation has become.