I think SE needs to focus on making players feel important again.

[Jeeqbit]

just introduce more branching pathways

Do you think this has been successful in variant dungeons?

They could just extend the variant dungeon concept to normal dungeons, but I also find it a bit boring redoing the dungeon over and over slightly differently just to see different outcomes.

optional mobs that lead to coffers

We definitely had this for ARR. I would say that more than 99% of the time, these were skipped and still are.