Title.
Like, holy fuck, why?
Completely unacceptable, in my opinion.
I know your pain. And I gotta go to the local tornament at Nintendo Center in a few hours..
It's especially odd when you consider that the controls are simple, consisting of an x-y position (joystick) and 6 buttons(abxylr). After sending a control scheme at the start of the match, they could send the full set of controls for only 70 bits per player per frame, or 4.2 Kbits per player per second. Even with 4 players, that's a maximum of 16.8 Kb/s, which extremely low, and should work on any connection. They might also need to synchronize the RNGs, but that could also be done at the start of the match.