Yep, nintendo is really making a game for kids. And the Salmonids have been terrorizing Inkling kind for centuries, destroying their cities and massacaring anything in their path......... Rated E10+ my ass.
Personally I'm trying to avoid spoilers on the single player campaign until I get a Switch and the game itself. I'll probably get it as a Christmas gift, though, so that's months of dodging spoilers for me.
