It sucks, but a 3 minute guide on your role in a particular M+ dungeon will teach you everything you need to know and watch out for. If people would just learn something about the Dungeon mechanics, we wouldn’t need these topics to exist.
Even 3 minute guides, addons, and the top WA don’t prevent players from standing in Detonation Seeds, Flames of Doubt, or other very very telegraphed attacks, but the little details you can learn in a quick guide would see a sudden surge of players not flopping as much
Again, it sucks, you shouldn’t have to go outside the game to learn about every critical detail in a M+, but there isn’t a great way for Blizz to provide a resource for it either, as that would then become them directly telling players how to play the game. Dungeon journals, even though players ignore them to this day, provide great information about bosses–but I would argue that the Dungeon journal should include trash mobs, and the critical moments to watch for.
Blizzard was a big fan of, Tank Busters, like Dark Claws, Hanuting Gaze, Severing Slash, Mortal Hew, Arcing Strike, etc that are designed for hard stuns/blinds stops, and somehow, players even in the 2700+ bracket have failed to catch on
Edit: all of this is to say that a penalty for leavers is not the solution. Sometimes the group just plays a bad game collectively, or someone in particular keeps messing up, but, you simply will not time these dungeons with 1 person underperforming.
If you find yourself stuck in 2k-2.6k you need to make friends who you can play and communicate with. You are only going to have a miserable time listing 18-20 keys for pugs to come and brick because y’all DO NOT communicate with each other at all.
And if you don’t care about any of that? Always list your key as completion