As someone who is relatively new to D&D (started playing in 2001), I wouldn't know anything about planescape if I didn't frequent this board and the WotC boards. Or, I might remember Planescape: Torment, but that'd be it. Out of the 4 groups I have been fortunate to be a part of, only people in one knew anything about more than two of: Greyhawk, Ravenloft, Forgotten Realms, Spelljammer, Planescape, and Dark Sun. And that's only because they had been playing since 2e.
I personally like the changes they are suggesting, because it's close to what I do when I homebrew.