Firehopping was a clear design flaw the developers overlooked, so why should anyone be surprised that Nintendo fixed their mistake? MK8D may be seen as "boring" now without firehopping, but that's subjective, and subjectivity is something Nintendo doesn't give a fuck about. Anyone who's crying about the removal of these imperfections can just stop because your crying will not change a damn thing. Instead, use common sense and just continue playing MK8

Remember:
MKDS players abused snaking -> MKW and onward removed snaking (and manual miniturbo charge).
MKW player abused bikes' clear dominance over karts -> bikes suck now (or perhaps in MK8D, equal).
MK7 players abused gliderboosts and gliderbounces, as well as boosts from entering water -> MK8 made gliders shit, and entering water is slow and shitty
MK8 players abused firehopping, momentum slides, and wheel/dpad -> all these techniques are removed from MK8D.
*Glitches are also impossible in MK8 (and MK8D), something that hasn't been the case previously.
So again, this change can't be of any surprise.