I think that folks looking for classic+ aren’t looking for TBC content, but instead are looking for new content designed with classic design mentality to be added.
This is a very different thing than just leveling to 70 and playing TBC.
The issue with classic+ is that it would take a LOT of work. And quite frankly some people ONLY want vanilla. So adding in classic + already would have to have some sort of separation otherwise it would be a big middle finger to those who only want vanilla.
What better way to split up these two things so everyone is happy besides TBC?
Don’t get me wrong, I’m not saying adding another raid or dungeons is trivial, but it’s really just confined to mechanics that exist in the game already.
Truth be told, they wouldn’t even need to add any additional gear. Take what exists in the game and spread it out over the bosses in the new dungeon/raid. If all you want is what’s in classic, you’re free to choose to not partake in those.
I suspect, though, that people saying they don’t want these things still crave new content to explore, even if they won’t admit it. Running the same thing over and over for no benefit isn’t something very many people actually want to do.
Anyway, not saying that’s how classic+ needs to go down, but it might be one way.