At least there's a perfectly good reason why to be upset.
Still really sucks for the Wii U. If technical problems truly were the culprit, it would not have been a good idea to released a botched version on a poor-selling system that would not only run better on other systems, but is guaranteed to be more profitable on the newer system. But the unfortunate side-effect of disappointing and angering Wii U pledgers was inevitable. It's all a double-edged sword.
I really hate why Nintendo opted to go for weaker hardware for no good reason. This is partly their fault, too. *facepalm*
I'm very sorry for everyone who would rather a Wii U version, honestly. I know how it feels. I've been there a few times.
The system was dying anyway. Nintendo has cut support, the Switch would be available a month before the Wii U version had come out, and nobody wants a Wii U anymore anyway. It's in the dust now. Many predicted the Wii U's demise even before the Kickstarter finished. We should have prepared for this possibility ages ago.
On a more positive, slightly selfish note, I pledged for the Wii U version, but I'll be getting a Switch anyway, so this doesn't affect me too much.. Now I won't have to put up with the Wii U Pro Controller's horrid face-button placement. Bring on comfy control layout!