Hi, I'm an ex-hardcore raider through all of WoW's history. I did Karazhan, The Eye, SSC, BT, Hyjal, Funwell up to Mu'ru. I did Naxx, Ulduar, ToC, ICC. I skipped Bastion, but did Firelands, Dragon Soul. I did MSV, HoF, ToT, completed SoO. For most of these, I ran progressive heroic content (where available). All of these were done when relevant and I have the achievements to prove it (with the exception of BC content from before achievements were a thing).

New dungeons are ABSOLUTELY new content. It's a new game. There isn't a lot out there yet. Honestly, the only really poor decision SE made was to release CT with lower-tier gear and bosses than BC as it means people who are endgame focused will likely skip it entirely.

Quit whining.