Default multiplayer voice-chat is the swollen appendix of shooters. It might once have served a function, but now it's a useless bag of pus threatening to kill everyone. Professional teams use third-party programs. People playing with friends use private parties. The only ones making noise on the default channel are:
a) using the microphone to help them swallow deep-fried oysters
b) neglected children so desperate for attention they'd take social tips from To Catch A Predator
c) those same children after 30 years of confusing kill-count for achievement
Multiplayer voice-chat should be off by default. That way you can turn it on if you want. The same way you can read YouTube comments if you want. A complete inability to speak still won't stop some people from being assholes, but Splatoon's fast matches and rapid rotation of teammates means you're never stuck with an idiot for long.