Riot u need a better anti afk system

So I just finished a game where we lost going 43/31 because a duo afked. I have 0 clue why they did, but they did.

http://matchhistory.na.leagueoflegends.com/en/#match-details/NA1/1727835848/43996950?tab=overview

I mean when we had a gold advatage even after they left for about 5-10 minutes and got an ace in a 3v5 it was obvious that we should have won. At least Valve will make the game safe to leave or something if someone dcs for 5 minutes. But I mean we could have surrendered and not even tryed to continue to dominate them and hope that we could push and win.

I mean really Riot. They needed Baron to kill a 3v5 because we just couldn't push when they an extra 2 people.

Something needs to be done. Whether it make ranked abandoning harsher or giving some kind of loss prevention or reduction.