Buildings don’t need to breathe, people do. Buildings need to dry out, and there are many ways to do this that don’t involve uncontrolled air flow that destroys energy efficiency.
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.
I think both of you are correct, you can have a tight building, but you need to have a way to get the moisture away from both sides of the vapor barrier. There are definitely been cases in the past 30 years were buildings were built tight without correctly considering removing moisture.
