Simple and same issue as Wii U: 3rd parties won't port many games to NX, and whatever they do will be regarded as inferior. It doesn't sound competitive for a home console.
Sure it doesn't have to be powerul for core Nintendo fans, but Wii U's sales tell the limit of that. To sell more than Wii U it needs to go well beyond appealing to the core fans. To have Wii like appeal it would need another catch.
As a handheld the device doesn't have to be powerful, and has potential to sell well like Nintendo handhelds before it... except the design if accurate shows a 6" screen which isn't handheld size... it's Wii U GamePad size.
It's always doooooom for Nintendo. Half of their share price came from their new mobile phone games... so if Nintendo listen to their shareholders it will become more and more a mobile game company.
