I’d love to see a world that feels alive.
This means that NPCs need complex schedules that look like they are contributing to the economy in the game. A farmer wakes up in the morning, goes to the field, harvests crops, carries the crops he harvested to the mill in the evening and then goes to the pub before going to bed. The miller grinds the crops to flour and bings the flour to the baker. The baker then bakes bread out of it. Miners bring ore to the smith who melts it and forges weapons and armor out of it etc.
If there are respawns in the game, make them logical. Monsters should not just magically reappear but there should be a logical explanation for them to reappear. Spiders could crawl out of nests, Bandits could move into the area to look for a new site for their camp, wolves come down from the mountains looking for prey etc. There could be some kind of ecosystem in which the animals and monsters live and which determines their behaviour.
Also monsters need a purpose to be in the place you encounter them in. Why is a Lich in those ruins in the swamp? What are the skeletons doing on this graveyard? If you encounter a bear in a forest, is hit trying to protect its cubs?
This would make the world feel alive and interesting and not like a static “set” like the set of a movie.