I didn't notice that knockback stuff you mention but that's probably because I didn't give it too much thought when I was playing it.
I think the low point is a couple of stages that suck balls. Along with the boss fights that are nothing special. The upgrade system gets useless fast too.
But aside from those sucky stages the ones that I did like, I loved them and the music was pretty good too! I do agree with you that a new game plus is something I wouldn't do, the stages that suck... they suck hard. I remember the underwater one and the one that's on an airship as being the most sucky.
"I've Underestimated the Horse Power from Mario Kart 8, I'll Never Doubt the WiiU's Engine Again"







