just today, I watched a video on how to permanently fix "joycon drift" (apparently the joystick loses sensitivity over time and starts drifting?).
So, this afternoon I went downstairs and got my electronics screwdriver kit, disassembled the joycon, inserted a folded-up piece of paper, and screwed it back together.
And... after testing with Sunshine, I'm suddenly good at the game again, making every move perfectly and completing levels easily.