The lobby should be locked after the game ends, preventing people from leaving for 30 seconds
This gives people time to talk about the game afterwards. Maybe in bronze/silver this can be disabled because clearly people don't care about the game in general, but this should be a thing in higher elos.
Discussing the game afterwards in post-game lobby helps people improve. It will make people look at the charts, talk to other people what they did wrong ect.
As of right now inters/feeders leave the game immediately. They never actually want to learn why they're doing poorly in games and this could solve that.