Mario Kart 8 is such a fucking great game, but I really, really want to see more single player content in these kart racers.
It's a tired argument, but this is why Diddy Kong Racing is still my gold standard. Not because the core gameplay is necessarily the most balanced, but the three vehicles swapping between races, explorable HUB, discoverable secrets, boss races, etc, alongside a couple of unlockable characters, made for a super engaging and exciting single player experience. Mario Kart DS is the closest from Nintendo to hit that mark, just because if its regular rotation of challenges.
This is actually what excited me most about that dumb Star Fox Grand Prix rumour; the notion it had a Diddy Kong Racing-like single player component.