Well typically what I have to say to complaints like these is that :
You should only be allowed to complain if you have NEVER won a game due to AFK on the enemy team.
In which case, I would sympathize. But I find it hard to believe that in the current games where everyone seems to have problem connecting from time to time, that you have never won a game due to it being 5v4 in your favor.
On a side note : 24 LP has nothing to do with AFK or not, it's simply based on the average MMR on the team against the opposing one.