looking from the outside (thank god), Kessel isn't "the problem". "The problem" is a one way player on the wing can't be your far-and-away best player.
It's not his fault, it doesn't mean he isn't good, but it does mean you're not going to win. The leafs need to trade him because he's one of the pieces that is actually worth something. That has somehow manifested into a 'you can't win with Kessel' narrative.
I look forward to seeing the fans railroad him out of town, than bitch about what they traded to get him vs what they get in return. Should be good fun.