Value is not the same as appreciation, which is what we're talking about. The value in a structure is the use one can expect to get from it over the next twenty years, or however long it takes to completely depreciate. GP is correct, especially so for 90% of homes built in rural areas in USA. These stick & drywall homes will have major problems within 50 years of construction, period. Many will require major fixes before then. Some homes in urban areas are built better.

The metric is an obsolete simplification, not the actual market.

You better tell that to the buyers, sellers, lenders and tax assessors who define that market.