I appreciate the thought you put into your post, Kairon, but how would Nintendo's android store be any different or better than Amazon's, which is run basically the way you described? I find the Kindle store to be very disappointing compared to Google Play, and I see Nintendo's version of the store being the same way.
To your other point regarding Steam on a Nintendo console, I'm not sure Nintendo's profit margin is all that thin on their hardware. I recall seeing some very detailed arguments as to why Nintendo will never abandon hardware, and as I recall a healthy chunk of their profit actually stems from actual hardware sales and not from software sales or software royalties (via 3rd party software).
From my vantage point, having next to zero third party support and allowing someone like Valve to cash in a little on what third party royalties you receive is kinda like the exact same thing. In other words, unless Nintendo intends to have a ton of third party support via their hard earned efforts to repair relationships, it'd be better to invite these other stores onto their platforms just for the point of offering all that content as I'm sure it would help move some more consoles.
On that last point, I maybe wrong, but having access to the Steam library seems attractive to me, and Nvidia's Shield already had that baked in, so having it on the Switch would seem to be a simple achievable concept. Why would anyone not want that?