Nobody else is okay with a cartoony Metroid game because Metroid isn't cartoony, it's a game about a woman who was adopted by aliens after space pirates murdered her parents and who trained until she became a deadly bounty hunter with no feelings on a quest for revenge. That's not a cartoony woo-hoo feel-good kick-a-ball-around plot, that's pretty dark for Nintendo. They've done it once with Zelda and the series still hasn't recovered from its toony rut, now they're murdering their last mature IP and people are understandably upset.
This is exactly what I mean. You sound like my friend who was butthurt that Diablo III had cartoony graphics. It's supposed to be a fun spinoff. I highly, highly doubt it'll be a canon Metroid game. Do you hate Metroid Prime Pinball too cause it's not MATURE enough for you, buddy?