While I get a lot of what you say concerning 2D Mario vs 3D Maro, I don’t understand why you never mention “Super Paper Mario”, a 2D Mario platformer that has been out for the Wii almost since the start. If you want to say that consumers weren’t focused on that kind of game at the time, okay. But you keep going on about Nintendo not making a 2D Mario for the Wii, yet they already have.
Super Paper Mario is a Paper Mario game. It is the third game in the Paper Mario series.
No one considers Super Paper Mario a 2d Mario game in tradition of the NES and Gameboy classics. Super Paper Mario is just a very different game. 2d Mario is an arcade type game. Super Paper Mario is an RPG type game which would never work in the arcades.
Only parts of Super Paper Mario are in 2d. Much of the game takes place in 3d. Also, the game is not action based or platform based. It is more puzzle based. Super Paper Mario has more in common with Mario Galaxy (which also goes into 2d at times).
I bought Super Paper Mario when it was released based purely on the hope of 2d Mario gameplay. I was sorely disappointed. The idea of a 2d Mario RPG is really grand and could have been amazing. But Super Paper Mario was nothing but lots of text and incredibly dull gameplay. Just recently, I’ve tried to get into the Paper Mario games but can’t because they are so dull to me. Most RPGs can be dull.

Too much text!
Super Paper Mario wasn’t a good RPG and certainly wasn’t a good platformer. 2d Mario means 2d platformer in the spirit of the early Mario games.
It is frustrating being a fan of 2d Mario. Miyamoto and all know that 2d Mario sells. Yet, after almost more than a decade of no more 2d Mario, games were coming out from Nintendo flirting with 2d Mario. Super Mario Galaxy frequently went into 2d mode constantly. Super Paper Mario was made only because someone at Nintendo had this idea that switching between 2d mode and 3d mode would be “really awesome”. I hated it. And sales show Super Paper Mario not going anywhere.
After a few days it took to finish the game, I sold it at a used game store. Extremely disapointing especially considering what great potential a true 2d Mario RPG could have.