Nintendo magic doesn't exist
What exists is great expertise and virtuosity in some genres, like platformers, because of the employees they have and the experience they have doing those things. They also have some geniuses like Miyamoto.
Mainline Mario has continued to be great after Miyamoto (after Mario 64) because Koizumi seems to be great, but Aonuma with Zelda does not seem to be as good as Miyamoto was (his last Zelda was OOT).