This comes up every so often. The reality is that there's lots of new ideas, but Nintendo just put Mario or Zelda characters into it.
Does Mario and Rabbids count as a new IP? What about Super Mario Wonder? The new Zelda game? Splatoon? Arms? Captain Toad? Mario Maker?
So really the question is, should Nintendo create new characters/settings? Does it matter if every new Nintendo game is in the Mushroom kingdom, with Mario characters playing Tennis, or a pile of mini-games? All of these games play very differently... so I'd say that all of these games are new IP...