comment: The Wii is one of the highest selling consoles of all time. It is and remains immensely popular, and I do think that if you are consistently seeing people trash it, then you are in some rather niche circles. 
  But, as far as the Gamecube, there is good reason to try and lift it up. The GC was not popular on release and it did not capture the public nearly as much as the Wii, as you acknowledge. So, a lot of the people you describe going back to it are likely people who never played it as a kid and are just now experiencing it's great library of games. Most people have already played their favorite Wii games and have moved on.
  Plus, this is just anecdotal, but I hear my friends and such have nostalgia for the Wii all the time. They were hyped for the switch remakes of Wii games and go back to play it much more often than any Gamecube games. It may just be a generational thing, but I do not experience the narrative you describe at all.