I just saw this and I was curious, so someone please tell me!

did you try clicking the "view rules tab" Kappa

Legacy is the original 32 tracks of MK8 Wii U without the DLC/Bonus tracks. I believe we're in the process of adding a 32 Tracks (Deluxe) leaderboard, which is using any 32 tracks as opposed to the original 32 tracks of the Wii U version, as all 48 tracks were available upon Deluxe's release.

It’s gone

Nah, the tagline has simply been removed. Instead the rules for 32 tracks have been slightly revised to add some more clarity into the category. It's still the same category as before.