I started during Vanilla but didn't raid until WOTLK... And after languishing during wrath bouncing from guild to guild looking for a good regular raiding spot, Cata hit. I've been able to raid about 100x more than I was in wrath and I'm not even talking about LFR. For whatever reason, Cata normalized raiding on my server. I've raided and raided and raided with ONE guild during this expansion... My theory (just a theory, relax) is that LFR made casuals more comfortable with doing normal raids. Casuals were able to be introduced to endgame content and as a result, that content became less intimidating.

So my experience is exactly opposite of the claim the OP is trying to make.