The problem with Nintendo going third party outright is I don't think they'd simply be as good of a company that way.
They wouldn't bother to try ideas like Splatoon or ARMS or bring back niche IP like Kid Icarus or Pilotwings or Punch-Out! etc. etc.
It would just be Mario/Mario Kart/Smash/Pokemon/Donkey Kong/Kirby/Zelda and maybe Metroid once in a while over and over and over again, just like companies like EA only make FIFA/Star Wars/Battlefield/Madden NFL/NHL, etc.
When you don't have any responsibility to a hardware platform, you have no real responsibility to growing the user base.
It's not like the Switch games look awful or anything, Zelda and Mario and even ARMS all look quite pretty. Would I prefer them running on a 1 TFLOP system at least? Sure. But I do like we are actually getting a real trade off this time in portability ... now I can play these games on long flights, to me that's a big plus, whereas the Wii/Wii U were underpowered for the sake of a controller, and that wore off real quick.