It wasn’t just marketing fail. They failed to get developers on board and failed to player test adequately, a mistake that Nintendo consistently makes in cycles. N64 and Gamecube should’ve taught them but finally it seems with Switch they’ve gotten the message.
The Wii-U is fine but severely underpowered and the tablet was very limited in range and capability. I have one and enjoy it but it simply wasn’t impressive from a hardware standpoint and it wasn’t clear what you were supposed to do with it as an end user. Sony & Microsoft also ironed out their online gaming experience while Nintendo continue to flounder. That was a really important market in the 2010s and they completely failed to capture any of it.
The PS4/Xbox one just blew it out of the water performance wise. The tech gap was too wide (the CPU was a serious bottleneck) and it was a pain to develop for them when you could just develop for PC and/or PS4 and/or Xbox.