More Animal Crossing stuff please, especially the 24 hour store.
Also a couple more variations in the store stock and buyable bait would be nice. I visited other islands back when people here were more regularly playing, but now I usually find myself watching the skies 'cuz I'm more likely to find something I don't have in a random balloon than with Redd's load of all of two furniture items or Wisp's "How about a wallpaper or flooring this time" self.
As for other stuff I'd love to see...well, here's a few things.
Mild: The option to buy a 10-pack of Nook Miles Tickets.
Medium: More camera options. Aperture, focus, rotation, new filters and frames, that sort of thing.
Hot: More returning old villagers. I would love for the pirate pig or the Squirrel Sisters to return. Also more brand new villagers. There's room to expand, we still don't have a peppy deer or a sisterly hamster yet and octopi are underrepresented. Hell, get some lionesses in there so lions aren't exclusively a boy's club.
Spicy: More interactability with objects in general would be nice...but I'd settle for just being able to ride the kick scooter or mountain bike.
Extra Spicy: I understand if this is too much for the current game engine to handle, but...Allow the player to break off the grid. Real-life objects don't work like 90° squares and rectangles, and especially with a photo mode I would love to have far more control over object placement.
I want to tip the garden gnome over. I want to put more than four glasses of sparkling cider on a single table. I want each individual chair to be off-center in one way or another.