The issue with the Wii U is that there was no demand for the lineup. The games coming out were all inferior versions of stuff available on other consoles. Wii and Switch both offered new ways to play the games that many people preferred, and that is why the demand was much much higher. Both Switch and Wii had far stronger exclusive content as well. You can slap on a 90 score to as many ports of AAA games as you want, but if they’re the same or inferior to what’s on consoles that everyone already has, and don’t offer anything new, people won’t want it; to the general gaming population, those may as well be 3/10 games shovelware games (which they technically are). The Wii was a unique case where many stubborn review sources were out of touch with what the general gaming community found good; ignoring how much more interesting the interface changes made the games; RE4, Scarface, and Godfather are all early examples of uniquely awesome exclusive experiences - the Wii versions were WAY more fun than the others. Many people who would never consider playing a golf game got Tiger Woods PGA due to the motion controls.
Then there was the party gaming component. The Wii was by far the best party gaming machine in the history of the industry. Local multiplayer has not been as big before or since. Perhaps the Switch can change that. I have been finding the portable nature of it is allowing for big local multiplayer situations. This is why Mario Kart 8 has become such a success on the console; it’s a better fit for Switch than Wii U.
I describe myself as a little dose of toxic masculinity.