It's my belief that the underpinning design principles have not been lost - cathedrals are quite well studied by architects as I understand it. So, while some

It's my belief that the underpinning design principles have not been lost - cathedrals are quite well studied by architects as I understand it. So, while some of the specifics are probably having to be identified and re-implemented, the basics are broadly understood. Stonemasons as a mass-employer has gone away, but like blacksmithing there are still individuals out there who carry on the tradition.