Damn lies and statistics
Given that the commercial aircraft accident rate in 1970 was just over 11 per million departures compared to less than 1 per million departures today, the statistics suggest that the old reliance on common sense and good airmanship wasn't as good as some people think it was.
And, yes, before someone points out the improvements in technology this is, of course, a major factor as well.
If done properly CRM/ HF should not just be about the illustrious aviators who take to the skies. If it's carried out as part of a proper SMS it is as much about improving the organisation that supports those that fly so that decisions makers, whether in the cockpit or not, are able to make the best choices possible in every situation.