Leaver punishments are a band-aid lazy fix for actually serious game design issues that cause players to feel like leaving is the best option on the table in front of them. The fun part being people actually just try to find ways to avoid the leaver penalty, and they still continue to avoid running the dungeon.
Take World of Warcraft mythic plus dungeons for example. You get to a point when all you need from dungeons is the score. The gear or resources you would get from the dungeon progress you exactly zero, so all you care about is finishing the key. SO of course people are going to just leave the second the key goes bad, they are only there to have it go good.
They added the leaver penalties and what happened? Well people now vote to end dungeons, and when people vote no and force the person who wants to leave to play. He just AFKs, was anything actually solved? No.
So we need to look at the reasons people actually leave this game. I think the main offender is people are not able to actually queue for the dungeon or tier they actually want to run. This causes a massive issue where the role with the lowest queue time will just keep leaving until they get what they want. You can fix this by letting people queue for the exact dungeon they want.
The second main reason people leave is the group simply isn't doing well. From my experience from pushing multiple characters, is that the DPS role is extremely important, and having weak players in that role will cause you to fail nearly 90% of the time. There needs to be a better climbing system that holds back players that are not actually learning the game. Both the tank and healer role are currently pass or fail, it's only the DPS role that can climb without actually getting any better at the game. What would this look like? I think the game should teach DPS very early on that interrupt isn't an option, it's mandatory. Have dungeon climbing be based on rating, and lock 50% of DPS rating behind 1 successful kick.