Lose 21LP becoz a stupid kid afk

I played a gold rank game tonight and our support afk because he said we cant be the carry role. Then he left us since the first 10 mins. The team couldnt win 4v5 so the enemy kept snowballing after 20 mins, 2 of my teammates afk with support we finally lost the 2v5 game and I lost 21LP

Riot really need to work on this. So many trollers or afkers in rank game and causing people losing LP. People leave or afk just because they lose early game. I really hate that kind of people I believe I am not the only one who have this problem. Its hard to make rage kids not afk in game but at least dont let us losing so many LP just because of these people.