It's just human nature... when there isn't anything to talk about, people will look for things to complain about. In this case, it's Wii U. This time last year, it was the doom and gloom over the PS Vita. It had just launched, sales were fine, but they plummeted after the launch rush died down.
People always focus on the negative. It's in our nature. Sure, it's annoying to see people complain over and over again when Nintendo has shown themselves time and time again to overcome the odds and not go third-party or software-only. But, what can you do? Like 3DS before it, people who say Wii U will be the death of Nintendo will be proven wrong yet again. It's the same thing over and over again, anytime there's a new system.