If your team is bad that often, then probability states that so is the other team, except that without you, so an extra player who may or may not be bad. Actually, mathematically speaking, the other team is MORE likely to be bad than your team because of that extra player.
There is no global conspiracy that ensures that your team is always bad and the other team is always good "9/10" times. If you weren't penalized for leaving at low ELO, then with the general mass perception of ELO hell, then EVERYONE will be dodging games nonstop, and you'll have to wait an hour to get a game in whether or not you dodged. Unless you're asking for Riot to put you in your own little special queue that puts only good-record players on your team and bad on the other team, you're complaining about something that's working exactly as it should work.
I sort of see your point, but I DON'T want to be put up against bads with bads on my team. How is that fair? I just have to hope my team is slightly better than than their bad team? I know Riot can't do this, but I wish it could somehow weed out the trolls and idiots so, even at 800 ELO, you could be matched with and put up against players and finally either climb the ELO ladder or fall down it because of SKILL, not luck that your team is slightly better than their bad team.