I disagree. Metroid, Breath of the Wild, Fire Emblem, and Xenoblade weren't designed for children. ARMS, Splatoon 2, Mario Odyssey were designed for general audiences, which includes kids yes, but they don't target kids primarily. Only Labo, Kirby, and Pokemon were explicitly designed primarily for kids. Labo's pretty much the only game where Nintendo came out and straight up said that its for kids. You don't need an M rating to target an older audience. Good advertising, aesthetic design, and quality gameplay have far stronger marketing pull than the black letter on the box. 

Can't say i agree.

Also an M rating just means that it isn't targeted towards children. 

Yes, an M rating is not targeted at children (even though kids still play M rated games anyway so...). My point is that, you don't need to chase a Mature rating to market a game to an older audience. You can do that with good aesthetic design, simple, yet attractive ads, and fun looking gameplay. Nintendo knows this, which is why even kid friendly games like Splatoon 2 and Mario Odyssey were marketed to Adults as much as children. 

No. An M-rating means it contains content that is harmful for children or is seen as such in society. Games with different rating can be targeted at adults but don't include violence, sex, whatever, but still aren't interesting or even not appropriate for children.

For instance in movies, take movies with G-rating in the US (G means general audience and is defined by the MPAA as "All ages admitted. Nothing that would offend parents for viewing by children."). Among G-rated movies you find 2001: A Space Odyssey, Gone with the Wind or Planet of the Apes. None of these movies is intended for children.

Not Really

I understand but i don't understand how that changes the image of Nintendo. Just because they market it to a general audience doesn't mean that the overall interpretation still isn't childlike. 

That is what Nintendo sells to adults. A childlike experience.

Nintendo doesn't really want to completely shake off that kiddie image, for two excellent reasons, first, actual kids market is very important for it, second, it knows that many adult Ninty gamers really love to revert to childhood, although many of them won't ever admit it.

Yes. Nintendo still likes to portray itself as family friendly. But the difference here is that they now know how to sell that family friendliness to Adults in a cool and attractive way that they didn't bother to with the Wii U. There's family friendly, then there's familes with small children only, Wii U fell into the latter. 

Agree, marketing is far better, but design choices have been too, this time they invested their R&D money, and the money gamers too pay for the devices, in an exclusive feature, the hybrid design, that buyers showed to appreciate much, much more than Wii U's tablet controller. But yes, bad marketing could have partially crippled an excellent design idea too, instead they marketed it far better and they are enjoying the benefits of sinergy between good marketing and good engineering.

Humor me. What insecurities are you referring to?

And does everyone who think Nintendo has a kiddy image fall under that view of yours?