Way, WAY too many dungeon quests end with characters jabbering on forever before you can turn in the quest and get your skill point. If your group of randos doesn't care to stick around for you to turn in the quest, you end up having to do the whole thing again to get your skill point. I roll a lot of characters, so this has happened to me a lot. It's super frustrating.
This issue isn't on the people who leave, it's on the system in place. What is the reason for this system in the first place? Is it there to close down instances and save servers? If that's the case, why not just make the timer 5 minutes long or something if removing it all together is completely out of the question. That should give people time to get their skill points or do any looting they missed out on.
I've noticed that new patches have focused a lot on little quality of life changes. This would be a HUGE one to fix. I feel like this has happened to everyone. It's super frustrating. You don't even need to rework systems to fix this. Just make the timer longer and it should be good.
Aldmeri Dominion -J'Ualizz - Siphons-Spirits - S'Renrij - Byz Only Sweeps - Winds-Roots
Daggerfall Covenant - Lucky Lakhim