“Maybe have it be better insulated.”
The point of diminishing returns passed long ago for that aspect of design.
Just keeping the coils clean can do a lot to make the refrigerator run better, but they often are not designed in a way that makes it easy to clean them.
I recently had to replace the water valve on my refrigerator, so cleaned the coils from the back side while I had it pulled out and opened up & was surprised how much more dust & pet hair I was able to remove that way.