WOW, what a devastating report. The reality is that regulators almost always simply don't have the people who have the kind of experience to be able to accurately assess the ability of organizations operating aircraft under a "Historically significant aircraft" designation to attain and maintain airworthy aircraft and operate them safely. It is almost entirely up to the operators to step up and make the commitment to do the right things. Unfortunately like the Collins B 17 crash and this accident some ( most ?) organizations are not up to the task.
Sadly I think the day when people will no longer have the opportunity to experience a flight in an amazing historically significant airplane is rapidly coming. Insurance companies and regulators are going to cover their butts by making it impractical to operate these kind of aircraft. Organizations who operate historically significant aircraft have to take a hard look in the mirror and up their game. One more high profile crash with passenger fatalities and I think it is over for everyone....