I really enjoyed my time with the Wii U (I like quirky games and the "droughts" didn't mean a thing to me, as I don't have tons of time to dedicate to gaming), but as someone who's been a Nintendo fan since the NES, it's hard to deny that the Switch is spearheading a Nintendo renaissance while the Wii U was an off-season.
OP, you make your reasons clear for the personal preference, but I think the amount of extremely specific personal reasons, caveats, and "if you do this" or "if you're like this" reasons speak to why the Switch has been received so much better. As hardware, the Switch doesn't require nearly as many caveats for either the average user or the superfan to find it appealing.
One thing I'd objectively disagree with you on, though, is "underpowered." Both the Wii U and Switch existed or exist in a market alongside the PlayStation 4 and Xbox One. Based on its architecture alone, the Switch is a far more modern piece of hardware than the Wii U. When your console is 6 inches wide, running lower-res versions of current-gen games like Doom and Rocket League ain't "underpowered."