I don't think Nintendo really cares as much as it might seem. Sure, they try some partnerships here and there, but there's one thing they've never given third-parties, which is the one thing they want: hardware. Nintendo hardware is and will always be designed around Nintendo's own needs. They don't offer the power, controller, online infrastructure, etc. that most publishers and developers want, which is the main reason they haven't gotten as much support the last three generations, and likely never will again. Nintendo doesn't design their hardware with third-parties in mind, nor should they.
Nintendo may toss out accessories like the Circle Pad Pro for third-parties, but all-in-all I don't see how Nintendo have suffered with the types of partnerships they've tried with third-parties.