MapleSilver
Frost Egg Collector
Villagers not randomly moving away. I'm so glad they finally got rid of that in NH. It actually led to me playing less because being forced to check my town felt like a chore after a while. If New Leaf had the same moveout system as New Horizons I probably would have played it far more consistently.
Outside furniture is another good one, though I'm not sure the 3DS could handle that many objects at once. The Switch already lags when you have too much outside furniture so imagine a handheld console from 2011 trying to do the same thing. Outside furniture is my favorite part of New Horizons though, so if New Leaf had that feature it would definitely be my favorite Animal Crossing. Yes I know PWPs were a thing but they were so limited in comparison.
Outside furniture is another good one, though I'm not sure the 3DS could handle that many objects at once. The Switch already lags when you have too much outside furniture so imagine a handheld console from 2011 trying to do the same thing. Outside furniture is my favorite part of New Horizons though, so if New Leaf had that feature it would definitely be my favorite Animal Crossing. Yes I know PWPs were a thing but they were so limited in comparison.