even if a magical system could know exactly why someone left at all times with 0 wrong calls.. Then the toxic guys would just afk in the dungeon to not get punished.
And if you then punish people who get the afk tag, but only if they do it maliciously instead of have something urgent to take care of, the toxic guy will start jumping every 4 minutes
And if you then punish people who do that and somehow don't punish the people who do it because the key was dead anyway and are just chatting on voice, then the toxic guy will log off
and repeat forever.
There will never, *ever* be an automated system that punishes all the malicious actors without hitting any innocent people. So Blizzard has done the best they can, and that's nothing at all, because nothing is better than something in 99% of cases