I'd say the first thing is that the actual racing is a very minor part of the allure.
As they also said in this Direct the "main event" is the City Trials game mode.
Phase 1:
You get thrown into an open world with 16 other players. You explore it for ~5 minutes to find new ships/karts and powerups for those ships/karts and also try to destroy your competitors ships/karts and steal their powerups. Lots of different random events can also trigger at any time, like a meteor storm etc.
Phase 2:
The actual competition is selected and you can vote for the one that best fits your ships/karts abilities/powerups. This can be a race (speed), but also something entirely different like seeing who can fly the furthest (endurance), trying to hit a dart board (accuracy), battle royale where you need to destroy each other (power) etc.
I think that's the main gist of it. Been a loooong time since I played the original but it was super fun back then. Hopefully it holds up in this one.