17 years, if you include the Japan-only Tomodachi Collection for the DS.

Yes. And an environment like Microsoft wouldn't think a dormant, niche franchise like that would be able to achieve an overwhelming success after 2 generation.

But sure, if you want the last new IP, Nintendo has played it safe with Arms and focused more on bolstering dormant IP's on the switch. With Animal Crossing and Zelda in particular finding new winds. Splatoon was their last huge success as a new IP in 2015.

Labo came in 2018, but I have no idea how to evaluate the success of that.