You're sort of wrong here and the proof is the massive graveyard of homes built in the 60's, 70's, 80's and early 90's before we really understood new technique

You're sort of wrong here and the proof is the massive graveyard of homes built in the 60's, 70's, 80's and early 90's before we really understood new techniques and materials that were being used to build homes. So many of those homes rotted out and rotted out quickly. It's similar to all the moldy basements that were finished without considering that water vapor that can't escape is the real killer. Open up a 100 year old house that has been maintained and you'll see pristine lumber that has hundreds more years if allowed to not rot. You could take an old house and bring it up to a modern standard but you would never recoup those energy savings both in terms of the cost to upgrade and the energy used to create and transport those materials. Even just replacing the single glazed, wood windows that have an uninsulated weight box with modern windows is probably not worth it if the existing windows are weatherstripped (the most important thing) and have storm windows.