Idle:
This state of affairs is undermined by the obvious amateurishness and ineptitude of those responsible for the Shoreham display as shown in the AAIB Special Bulletin.
I don't read the SB in the same way you do, nor do I think you can criticise the organisers as being amateur or inept in this way. The FDD had every reason to believe that the arrangements were compliant with CAP 403, and it is instructive that all the AAIB recommendations are addressed to the CAA.
As Sillert notes in his comments about the Challenger accident, the risk assessments were shown after the event to be flawed (and it is always easy to be wise with the benefit of hindsight); like Shoreham, Challenger resulted from a process problem rather than amateurism or ineptitude. Tragic though the outcome was, I don't agree that Shoreham 'exemplifies a decline' in professionalism or safety standards, but it does show clearly that the regulations and guidance being applied were not adequate for the task in light of today's understanding of risk.