It's not their fault that they profit off stagnation, everytime they try something new it's called "not Nintendo" and seen as unsatisfactory. Take Geist for example, that was a great concept and really enjoyable I felt, but it was way out of Nintendo's realm and was immediately slammed. If it were made by say Konami, I bet it would have got much higher scores and better reviews.
Nintendo went for the casual, non gamer demographic because they don't have these fickle expectations from Nintendo. Like everyone said, "what do these people know about videogames?". It's for exactly this reason that I think Nintendo wanted to bring them in, because they could start completely fresh without their new consumers wondering where Ganondorf is or why Luigi and Yoshi aren't in the latest game.
Remember we have these expectations because we were raised on these concepts, but with a newer generation (kids love the Wii too) of gamers, there's a whole new scene to develop and explore. It's all just a cycle, and Nintendo went for simplicity because they're jumping right back to square one. I really do feel the next generation Nintendo will bring out a "core" pleasing console, because computer games are like chilli, after a while the same level loses its spice and more needs to be added for you to enjoy the same sensation. Nintendo is going to start pushing more depth into their games because obviously new gamers are going to want a bit more out of their experience.
They haven't hit a brick wall, they've hit the ****ing jackpot because they have brains enough to understand what a generation cycle truly is. It's about the age of consumers. Simple button layouts and easy to pull off manoeuvres, wasn't that what we grew up with with our Arcade games, Gameboys, NES and SNES?