I will let you argue the causes of various accidents. Except to say if you believe poor airmanship was the only cause of the 707 accident that would be a very simplistic summation.
A high flying rate isn't an excuse for the accident rate that was occurring in that time frame. I would agree with a older generation of aircraft may have an effect but that doesn't account for the number of people being killed at the time.
I can't find a copy of the poster, but if I do I will post it here.