How is backdooring a non-toxic element of the game? How is it fun that a team keeps getting stomped over and over in a 4v5 teamfights, only to win because the missing member has high mobility and was busy destroying the enemy base?
Take this Nidalee in my last game for example. Only 9k damage done to champions, going 2/2/3/305 in a 37 minute game (final score 21-18), yet doing 185k damage total, and last hitting 4 towers and 3 inhibitors. She didn't contribute anything to the game, other than being a chore to go and clean up for the enemy team. She would flee at any sight of a champion, and no one could hope to keep up with, let alone kill. She would never join in team fights, except she basicly won them the game.
I'm sure she was having the time of her life, but how is this in any way shape or form fun to the other players? One team is having to deal with the low of just losing a team fight and all being dead or about to be, whilst the other has their euphoria at winning a fight cut short by looking at the mangled remains of one of their lanes on the other side of the map. What counterplay is there to this other than someone sitting out and guarding the base? Or concentrating on the map in the middle of a fight, ready to drop out at a moments notice and go defend?
I have no idea how this could be fixed, as several champions are notorious for doing this (Yi, Teemo, etc), and it's part of what makes them who they are when it comes down to team fights. You can't buff towers either, as it makes them difficult to legitimately push.
Maybe I'm just overreacting. Maybe I'm just unskilled enough to know the proper 100% surefire way to deal with backdoorers. But I'm still slightly pissed off.