Stop living in a conservative bubble, make aggressive strides to expand software development culture on a global scale, listen closer to third parties and the echoes of the market they are competing in as much as they like to think they're not, be attentive to rapidly changing world of technology and economics, and understand that an overwhelming majority of customers do not want to put down US$300 for an unappealing piece of hardware that has scarce releases of Super Mario in between shovelware when for an additional $200+ dollars they can get a system with significantly broader software and genre variety, routine software releases, and a strong promise of continued support into the future.
Nintendo exists on the same planet and in the same market as everybody else mingling in home/portable technology and software. This isn't the 90s, where a dedicated game machine that just does what it does and it's Sony or Sega or Nintendo or whatever is good enough. The way customers perceive and value both software and hardware has changed. The expectations have changed. The risks and rewards have changed. The development environment has changed. The economy has changed. The customer culture of buying hardware has changed. And all of these things have changed rapidly and dramatically over just the last few years.
Despite this Nintendo operates as if nothing has changed and they can keep playing the same game they've been playing for the better part of two decades, despite the competition they seem to deliberately ignore rapidly adapting and growing alongside the rest of the world. People do not want to buy a $300 Mario box. They don't want to buy this, and wait three/four/five months for the next noteworthy game, one that might not even be a franchise or genre they're interested in. Not everybody who likes Mario likes Zelda, or likes The Wonderful 101, or likes Metroid, or F-Zero, or everything else. And that just makes the situation worse, when someone can put that $300 towards another platform that's going to have far more software released far quicker.
It's an investment, for customers and shareholders, and at the moment Nintendo is a bad investment.