If I had to guess, I would say that people hate Nintendo because they feel Nintendo forgot about them. So they moved on to the other consoles or PC or maybe even mobile. Kids grow older. They want all the adult oriented games that are on the HD twins or PC. Of course they still like Mario and all the goodness Nintendo brings, but they would like to play that as well as the adult oriented games. Since Nintendo games are on no other system that makes it hard for some to take that leap with a Nintendo console.
Others just want to see the world burn I thinkk.