Pokemon needs to have a quest log.
USUM had a heap of little sidequests, some of which were actually really cool
https://www.serebii.net/ultrasunultramoon/sidequests.shtml...but there was little incentive to do them, and more importantly, people didn't know they were there. If there were an NPC in every Pokemon centre that gave hints about townspeople looking for help and gave a reward for completing every side quest, I think you could hugely expand the universe and encourage exploration with minimal effort.
