You can't just have nothing but mass market games. Should Nintendo order Intelligent Systems to stop making Fire Emblem because it's a niche title? That all said, ignoring the mass market is a mistake as well. No 2D Mario on the N64 and Gamecube was a mistake. And it wouldn't be a bad idea to bring back 2D old-school Metroid and 2D old-school Zelda. These games will sell to the hardcore as well.
The problem with the Wii is that Nintendo pretty much pulled the plug on it and the third-party developers pretty much gave up on it (the announced E3 lineup is so light) when sales figures show that Wii still tops the software charts. Just Dance 2 is over half a year old and it's the best selling non-bundled Wii game out there. The Wii is pretty much relying on old software right now. You don't just purposely kill off a successful console like that. Leaving money on the table.