The people who are bored currently are definitely burnt out, whether they believe it or not. There's more content then ever before if you look at the entire game including all expansions.
Wrath's intro era was extremely boring. One major raid, which was a complete rehash, along with a bunch of meh heroics without LFD. PvP was very imbalanced (DKs owned in 3.0.X).
Sound familiar?
Yet, in the Wrath era, there was a huge game growth. People are just burnt out. People are nostalagic. This happens every expansion and even happened in TBC. I remember all the "TBC is so freaking bad" and "This game is horrible now" qq when TBC was released. Apparently everyone else has forgotten.