Hear me out, okay? I always hear people point to the GamePad itself as the reason why Wii U failed: it drove up the cost of manufacturing (and consequently the MSRP for) the system, it scared off third-party developers not looking to deal with such overly convoluted technology, the system never really demonstrated why the GamePad needed to exist, and so forth.

However… just look at the limited specs of Nintendo Switch 1 & 2 in comparison to the competition. Do we really believe that the GamePad was that much more convoluted than developing for a system only capable of running Dark Souls at 720p on-the-go? And how come the DS and 3DS saw such strong third-party backing despite not only having the same issue of a second screen, but also far greater limitation on specs?

While I do not deny the need for the GamePad’s existence was never truly justified in the software, it was an innocent little accessory that — if really necessary — could ultimately be ignored by third-party devs. The Wii U’s issues go well beyond the GamePad.

Thoughts?

I think the gamepad still was one of the main factors why WiiU did not succeed. Not because it was bad, I think the pad was well designed. But it somewhat felt like they designed the pad before they conceived the game ideas that needed it. And the marketing almost exclusively focused on the pad leaving the actual console in the shadow.
So I think the pad needs to take some of the blame even if the tech was good and using it was comfortable.

You are correct ;)

With gaming, the reasons people give for the success and failure of consoles are usually wrong. Or they're failing to tell the whole story. In this case, the main reason why Wii-U failed was timing. Wii kids were still kids, just older. And when you hit that in-between age, you tend to want something a little... well... grown up. As gamers, we all know most of that is BS, that a great game is a great game etc. But not at a certain age. And this is why the Switch mainly exploded (and why suddenly, all those Wii-U titles that nobody wanted became best-sellers). The kids that were raised on Wii were suddenly in college, or out of high school, far enough away from their own faulty pathology, and with some of their own money to boot. It wasn't the form factor, although that did play a role. It was the timing. It's always about the timing. Always.

Also, if a console can pick up the "thing to own" moniker out of the gates, it's pretty much set in stone to succeed. People love to be cool. They need to be cool and accepted by their peers and society. So as soon as something becomes that, forget about it. The rest can just go take a lunch. It's over.

It was really a perfect storm where almost everything went wrong.

The Gamepad was a mistake in that it added to the system's cost while not really being a selling point for most people, but the long droughts, dreadful marketing, silly name, and a myriad of other factors all came together to spell doom for the system.

The GamePad was not the biggest reason the Wii U failed, but it is an issue. Driving up the cost of the console was a huge problem.
Wii U was rougher to develop for than Switch because of its PowerPC architecture and weak and slow CPU. Those were much bigger issues for developers than only 2 GB RAM and the GPU.