One island per console. This was not an issue on gamecube as you could just use a different memory card. Now you're forced to buy multiple consoles and copies of the game to enjoy your own island.
My gf uses my switch, and I let her be the main account for the game. So now I can't progress the story, i don't unlock new items the same way. We're forced to share resources which grinds progress to near stand still early on.
Game is pretty disappointing. Items are almost purely cosmetic. Very very very few game mechanics, so you're forced to grind EVERYTHING for hours.
This would be acceptable for a $20 indie game, but a $60 AAA title this feels like a slap in the face.