Mario Kart 8 - while fun in multiplayer - quickly became my "chill-out" game on the Wii U, and on the switch is following a similar tangent. You can at least try to unlock the karts (more on that later) via collecting coins, and try to 3 star the cups if you want as well.
Online is where the game really shines though. Idk why, but Mario Kart 8 (and now deluxe) always have fairly stable connections for me, and as such I have logged countless hours just on online play. It's a great option as well, and with the portability of the Switch I'm finding it's nice to just hop in, do a race or two, and be done after.
Finally, coming back to karts, if you've gotten most of the 100, 200, 500 coins collected ones, you can always go for the gold standard ones, via beating staff ghosts, beating mirror cup, and ... Collect 10,000 coins ... Which ill have to do again.