Really? I live in a mostly not very well-insulated 200 year old wood construction farm house and I find that there can easily be a 10 degree F delta between indoors and outdoors. I have heat for the winter given northern climate but otherwise mostly just do regulation by opening or closing windows.

Your house was built before the days of A/C so the builders probably deserve more credit!

My house is also in a forest so the sun doesn’t bake it. That might be part of it.