Anyways, I actually read every single quest text there was from 85-90. If you had done that, then you'd know EXACTLY why we are in Mogu'shan Vaults.
But I will agree with you on one thing: the raids do felt underwhelming, but not just recently. Ulduar was the last grand-scale raid in World of Warcraft with everything after it feeling like a glorified dungeon. Gone are the AQs, the Naxxramas', the Black Temples; Places that make you stop and just pan your camera around in awe at how massive and detailed the design is. Hell, Mogu'shan Vaults doesn't even have it's own music.