I voted for three options: Isabelle's announcements, Orville's extremely long dialogues, and not being able to do certain things when people are on your island.
1. Isabelle is still one of my favorite npcs and I love how she is always happy to see us and greet us when we log into game, but I strongly dislike how she plays so little importance in the game. She should be given more roles. For instance, she should announce what visitors are visiting for the day because sometimes I miss out on visitors like Celeste. When I am walking around and I don't run into them, I believe they aren't there and then bam! I log in again hours later and there they are--they were there the whole time but I didn't know. And talking to Isabelle should allow us to reset a villager's home (much like changing their unwanted clothes, but even this doesn't seem to properly work which is a big bummer).
2. Orville just....talks....way...too...much. His words should be shorten to the most important points. Sometimes I spam click because of the long dialogues and then I end up misclicking and have to restart the whole process again

3. We should be able to decorate our islands while visitors are on our islands. It would be fun and very helpful. Like let's say our friends are over and we want their opinion on where to place items so we place it by the waterfall or by the entrance area and they can tell us if it looks good or bad---basically, decorating together! And maybe our "BFFs" in game, are allowed to decorate with us which makes the BFF function even more useful. And also, let's say we have random people on the island, but forgot to fence off certain areas, we should be able to fence on the spot! ;-; I know that would have saved me from some unwanted incidents.