From my perspective, nostalgia isn't a dirty word. I realize that a lot of people use it like a big pointy stick to try to invalidate people's feelings about it, but there's nothing wrong with being nostalgic. In fact, I'd say someone would have to be a cold fish indeed if they don't have nostalgic feelings about playing back then. It's basic human nature.
People can look at the cold hard facts of TBC gameplay and say they preferred that. But anyone who had good experiences back then are also going to have nostalgic feelings for the entire experience. Everything from killing bosses, to mundane stuff like shooting the shit with people in guild chat.