Wasn't part of the problem with the Comet that it was a demonstrator
Exactly. Its a QA problem in that the process is part of what is being certified. And if that isn't under control, all the great engineering in the world won't save you. And the bad engineering won't get caught and fixed.
Boeing has suffered from time to time from management building a firewall between engineering and manufacturing. It has been, "Release the damned drawings and get out of out hair" all too often. Engineering's response has been to step away from the QA process and expect manufacturing to work around poorly thought out designs on their own. Back in my days there, manufacturing had their own 'shadow' engineering group to fix stuff that the design people tossed over the fence.