I think riot should punish ragequits extremly harshly.
Having an afk in your game is maybe the worst experience you can have in a match. I understand there is no way to completly prevent afks. There are players who have a suboptimal internet connection or pc that sometimes fails on them and I don't really think that they should be punished too hard.
But I have zero understanding for people who ragequit the game. Yeah the game might not be going well for you, but just quitting is the worst thing you can do. It completly ruins the game for everyone else. Even when the team is toxic, you have the mute button. In my opinion people who ragequit should be punished extremly hard, in extrem cases even permabanned.
How can riot distinguish ragequit from dc? An algorithm could probably do this job. Ragequits pretty much never happen when the player in question is doing great in the game. We just have to look at the kda, gold and lvl in comparison to the opposing player of the given role, at the point where a player is disconnecting. Maybe the overall gold/objectives of both teams should also be reviewed. And if there is a consistent pattern, that every time a player disconnects from the game he is extremly behind compared to his lane opponent (or enemy jungl), we can safely conclude, that the player is ragequitting, not just having a bad connection.