My house is larger than this, and my wifi covers my house, my yard, and reaches a few houses away. There's something different about your house, do you have metal in the walls?
But I agree with your basic point. An access point in one corner of the 1800 sq. ft. house mostly covers the whole place. I was just at a friend's 2BR Europen apartment and one access point only covered about half the place.
I DO have metal in the walls... reinforced concrete is a thing.