djpl, I agree with your sentiments, but not necessarily your perception of the facts.
Crashworthiness is a clear enough issue - that of minimising injury to aircraft occupants following an accident. Go back 50 years, and the consideration of this issue was extremely minimal, whilst nowadays it is a fundamental subject that must be considered during the design and certification of any aeroplane.
But it is an increasing issue. The latest generation of light aircraft are firstly a lot faster - and so the energy of any impact is potentially greater - something has to be done with that energy to stop it transferring itself into the occupants. Also a great many of these aircraft use advanced composite materials - post crash these materials emit all sorts of nasty stuff capable of causing both short and long term medical issues or causing death through inability to escape the wreckage.
An additional issue is that parts 23 and 25 use stupidly low loads when considering seat structures - typically about 77kg / 170lbf, so the structure may well not retain larger occupants. Some GA aircraft (mostly either UK developed microlights or US developed helicopters) are increasingly using much higher and more sensible numbers in this regard - but it is a crashworthiness issue that sooner or later is going to start causing problems.
BUT, old=good, new=bad, is almost certainly not true.
G