How on earth is the online so broken? London 100mb / 2ms here, wired connection, and probably 10 communication errors in the last few hours. Failing to find a match, failing to start game, failing mid way race. Shameful.
I think it might be other people's / Switch's shitty wifi causing a lot of the issues. Try the GAF tournament if you haven't, for me it's much less prone to disconnect me than global matchmaking.
But yeah, if they're gonna charge for multiplayer.... come on. Give us some damn dedicated servers.