I agree with you Nik, but they've had 5 years to think about it. Plenty of possible solutions have been presented though I'm not so sure how many are practical but I'm sure the community would be happy to present a lot more suggestions.
Thanks for posting that link. It says they MIGHT think about doing something about it in the future. I agree with you too, low priority queue isn't enough and it's not an in game solution. I'm not talking about punishing the players who have to leave for important reasons if it happens because stuff happens. The power could go out, you internet could suddenly stop working or simply just life. But when those sorts of things happen, something like a soft reset, or reduction of lp lost would reduce the frustration caused to the others who have limited time to spend and now have to waste 20+ minutes of their precious time. If people try to coerce other players into leaving the game because they're the feeder etc, that can be added to the automated ban system they have in place. Maybe this isn't the solution, but I'm sure they have plenty of talented minds working there to find one, if they ever made it a priority.
As Riot Lyte said so in the link, playing a game with 4v5 is "(arguably one of the worst experiences in League)". It doesn't have to happen often for them to affect you and upset you. It should be obvious why something should be done about this. I mean fix the basic stuff first, then work on the features. Would it really take that much effort to implement?