They said it themselves that they had underestimated the time and resources it would take them to develop HD games. Miyamoto said so if memory serves right,and I was like "D'Huh !! Seriously, you didn't know HD games took more time and resources?"
They hoped to have a lot of games in development before the launch of the system to be done at launch, or shortly after. Pikmin 3 was one of them, though you might argue it was in no way a system seller but more a magnet for fans of Nintendo and the franchise itself. I think they also hoped to have a couple more third party games launched as well, like Rayman Legends which got pushed back a lot. It was originally penned to be released 3 to 4 months into the life of the system and we all know how much it got pushed back (I remember it was planned for February 2013 at one point and was finished by then, too!)
Part of the problem, also had to do with being first to launch their system, delaying it too much would have placed them against competition on store shelves and I'm sure they wanted to avoid this. And the fact that people, LOTS of people got confused by the naming and thought it was just a new controller for an aging system didn't help things one bit. They didn't drive the point home enough, or should simply not have gone for that name. It's easy to understand that they tried to catter to the crowd who bought Wii, through brand recognition, but those people by the time the Wii U launched, had mostly already put the Wii in their cupboards and forgotten about it by then, so that didn't go according to plan either. Software and hardware sales near the end of the previous system's life, other than "Just Dance" fanatics, should have given them a hint to that effect.
Also... what are they hoping to do by keeping future projects secret ? "We have several games in development not unveiled yet". By not showing anything of what the future holds for Wii U and not building excitement on the long term, you only make people remember that Wii U exists when you make a Nintendo Direct or at E3 and the rest of the year, when nothing gets released for a long period of time, people forget about it. You should unveil them with less long stretches of time in-between each and then build hype with footage or pics more frequently, otherwise the games people keep thinking about buying in the future aren't going to be your own. What's for Wii U this year? Xenoblade? Zelda? Yoshi? Maybe Splatoon. Then what's next? By not saying anything all the time, you leave people with the impression that beyond those few games, there won't be anything left to play after that, and that's not a good impression to let people have. If people have to choose between a system like XB1 or PS4 which you can be sure will continue to be supported for years with quality software and a Wii U that's in permanent situation of seemingly not getting anything anymore, which one are you going to go for?
Starfox hasn't been shown yet. Kirby isn't a system pusher. Project Giant Robot looks meh. Mario Party 10 doesn't have online for crying out loud. And some of what IS announced isn't looking like big killer apps, sorry to say, like Devil's Third. At least not for me anyway.
My point is, they're not building anticipation and excitement like they should. I love my Wii U, I'll still be playing it years down the line, I still have a heap of games to play on it which I haven't even started playing yet, but I know not everyone is like me, and those people who don't have one yet, if they're not big Nintendo fans who can't live without their next Zelda, they're not being given big reasons to buy this one as their only current gen system, or even as a companion to a XB1 or PS4. They're not displaying the Wii U as a system that still has a lot of life left in it. Iwata's intervention is only throwing oil on the fire, because he's just teasing "yeah we have other projects you haven't seen yet", but he's not even throwing us a bone, it's just wind coming out of his mouth.