I think you can really judge how much of a down period the 2012-early 2017 era was by seeing how weak a lot of the core franchises were.

-Metroid's only release and 30th anniversary noted by a Federation Force game nobody wanted and that promptly bombed in sales.
-Star Fox's first HD game hampered by a Wii U controller gimmick that likely contributed to its failure in the market. -Animal Crossing reduced to shallow spin-offs or mobile games. -Zelda having no 3D games outside HD ports & with a forgettable Tri-Force Heroes release; with only Link Between Worlds standing out. -Mario spin-offs of various kinds (Party, Olympic Games, Sports titles) largely having lackluster or disappointing entries.

There were exceptions (mainline Mario, Kirby, & and Fire Emblem largely went unscathed) and there were individual games that stood out (Tropical Freeze, Woolly World, Smash 4), but it was a dubious time for Nintendo hype. The N64/Gamecube era had some interesting experiments, & the Wii Era had simpler but popular games; the Wii U era didn't have much of either.