What exactly in my opinion pieces are Flamebait?
I have never tried to label the Wii U as a bright spot in Nintendo history. My thread on the evolutionary path of the GameCube to Switch noted the Wii U's form function as a step (the final step) on the path to the successful Switch. Did I enjoy my Wii U? Yes, I did. I got use and enjoyment out of it from launch day through 2017. I've used it more sparingly since the Switch came out, but even recently I am still playing my backlog on it from time to time. But, I have never denied that it was a commercial flop. I don't know how you can look at the design of the Wii U's gamepad and the Nintendo Switch and not see the similarity and deny that the former was a step in the latter's direction though.
Did I enjoy my 3DS? Yes. Like the Wii U, I got both use and enjoyment out of it throughout it's lifespan. I can think the device was a success without somehow trying to twist history. The rise of mobile gaming was going to impact the sales of whatever device Nintendo put out into the handheld market. It certainly wasn't going to be able to come close to, let alone match, the 153 million sales of the DS. If the 3DS was a flop though, it would never have sold 70 million units and continue to be selling today. Consumers don't just go ahead and buy whatever device has the Nintendo logo on it, price cut or no. The Virtual Boy is indicative of that. What I specifically said, which maybe you glossed over, was that the 3DS is nearing Gameboy Advance level sales. Considering the climate of the handheld market, that's not a flop in my book. Sony's handheld sales dropped by 80% this gen. The 3DS was able to limit Nintendo's drop to about 54% from a much higher predecessor. So, yes, I think 70 million sales and counting, and being currently the 11th highest selling dedicated gaming platform is a success.
Easy. The Gamepad was about having two independent screens and Wii U was planned to be about at least three independent screens. Nintendo's intention was to sell Gamepads separately, but that never became a reality because they had so much trouble to sell the one Gamepad that came with the console. The Gamepad's purpose is very different from Switch's purpose, that's why Switch isn't an evolution of Wii U or "Wii U done right."
Considering what Switch is, it's safe to say that Nintendo identified the Wii U direction as a dead end, just like 3D which didn't carry over to Switch either.