I never got into SC so I don't really remember those courses. The only thing I remember about SC is horrific loose controls to the point where it was almost unplayable to me.
I think the problem was they were trying to pull off a 3D-style game on a system that was too weak for that. I never played SMK but from what I've seen it was the same way. I don't think Mario Kart was ready for handhelds until the DS
But GBA retro courses are fine, so I do hope the more unique GBA courses make it in to MK8 so I can actually enjoy them. Same for the SNES ones