If you think players are quitting because they are 'toxic' like your average MOBA player, you're insane.
Don't blame the players, blame the reason they quit and fix the heart of the issue, not a symptom of it.
Quitters would reach unprecedented levels if you could quit out of a match and have the game play it out for you anyways. Every single person with even the slightest disadvantage at the start would quit on the spot and let autoplay take over.
The player remaining in that game gets their free win and rewards for fighting what is effectively a PVE encounter.
The player that left the game is free to queue into another opponent. And if they are better then that opponent, that opponent will quit on them and they proceed to play out their free PVE win.
Every single game would have a quitter in it because the last lingering thread that might keep a underpowered player in a game against an overpowered player (the knowledge that quitting is harming the rewards of their opponent) is now entirely removed. There's not even a tiny blot on your conscience to make you want to stay in the match.
You would need some crazy systems to prevent that abusive behavior, like making ejection/game quitting cost fuel, and require fuel to play PVP matches.