Wii just lasted like a normal "failure" Nintendo console lifespan but it definitively did not lasted selling well as long as NES, SNES or DS, and it seems it won't last as long as Switch either. In its 6th year, Wii was selling almost 4x less than just 3 years before. NES, SNES, DS, PS, PS2, X360, PS3, PS4, all lasted more than 6 years, and they were not selling 4x less in its 6th year compared to its 3rd....That was unprecedented in a console that sold as well as Wii in its first few years. Every time you see a graphic showing sales of different consoles you can see how Wii drops in sales way more heavily than any other comparable console.
Despite N64 being considered a failure compared to PS1, Nintendo went from selling 49M with SNES to 33M with N64 and to 22M with GC. With Wii they went from 102M to barely 15M.
There's a reason why 2012-2016 are one of the least succesfully financial years for Nintendo in its history, and it wasn't because they started suddenly making bad games during those years (in fact it started their most creative years since N64 era). It's because Wii wasn't able to transfer their success into the future. I'm pretty sure more people are going to be hyped by the Switch successor than they were for the Wii back then.
And to explain my point, i was referring to motion controls as the use of nunchuks in Nintendo games. You don't have to play anymore Mario 3D games, Zelda games, ...only with just that technology. Nintendo backtracked and offered conventional gameplay as its main way to play the games. Yes, there's still motion control features (optional if you want), but you basically play most Switch games in conventional ways again and the most prefered way to play those games is with a classic pad style. Wii main characteristic was its Nunchuk controls. In 2006 it seemed this was going to be the next way of how to play videogames, but here we are in 2019 and people prefer a conventional pad again. I will bet my money, that most people prefer now playing their Nintendo games with a pad than with those nunchuks. That was the "fad" part of my point, the games in itself were not a fad, they were great in fact.
There's a lot of flawed logic necessary to arrive at your desired conclusion.
1. In your first paragraph you pretend that Wii's lifecycle is comparable in length to the N64, GC and Wii U, but it's actually similar to the SNES.
Nintendo's failures sold next to nothing in their sixth full year, because their fifth full year already made it clear that the consoles are on their way out. You also use a comparison between third and sixth year to point out something unprecedented about the Wii, but you omit that Wii's third party support was also unprecedented for a console as successful as Wii. I've talked about the importance of a healthy software pipeline with you before and there shouldn't be an argument that Wii's software pipeline was horrendous from its fifth year onwards.
2. In your second and third paragraph you blame the failure of a follow-up console on the preceding console. That's like making the argument that the PS2 was Sony's worst home console and the PS3's sales and financials prove it. Your argument is like saying that the PS3 is not responsible for its own struggles and that those tough years for Sony were caused by the PS2.
3. The huge error that Nintendo made with the Wii U is that they turned their back on motion controls and returned to the conventional dual analog setup with the Wii U Gamepad. The market figures that games for any given console will be designed for its main controller and the Wii U didn't have a motion controller. Unsurprisingly, the Wii audience didn't want to migrate to the Wii U because of that. The core of the issue is that Nintendo stopped making games like they did for Wii aside from a few token efforts in hopes to trick people into buying a console that isn't at all like the Wii, but that didn't work. The Wii didn't stop going; Mario Kart Wii added yet another 100k copies to its total during the quarter January to March 2019 while Just Dance kept releasing each and every year, meaning that there was a new game release for Wii twelve years after its launch.
If Nintendo ever releases a Wii Classic console like the NES and SNES Classic, it will sell very well because Wii's legacy is good. The same wouldn't hold true for Classic versions of the N64, GC and Wii U.
The preferences posted in this thread have no real value as far as real world reputation of consoles is concerned. It has been a common theme since the beginning of VGC that preferences and sales of Nintendo consoles don't align. Since sales predictions are often influenced by personal preferences, it isn't surprising that a large group of Nintendo fans on VGC had higher lifetime sales expectations for Wii U than Switch prior to their respective launches.