I think that part of the problem that we have these days is that air travel for a SLF has become a fairly miserable experience where passengers are generally treated like infants. The PA system is massively overused for things irrelevant to the flight (credit card offers, lottery tickets, et al) and as a result people tune out.
It's not helped by the fact that some of the safety demo content is particularly patronizing. Do we really, in this day and age, need to explain to passengers how to buckle and unbuckle a seat belt? Furthermore, is there really a value in trying to force a frequent flyer to listen to the same demo for the thirtieth time in two months?
On a flight not too long ago, while seated in an exit row, I was asked if I was over fourteen years old by a crew member. I look about fifty. The very fact that the question was asked is (IMHO) a symptom of what air travel has become.
Were it up to me, I'd have passengers watch the safety demo online at home before ever getting to the airport. They would then need to complete a multiple choice test on what they'd seen, and anything less than a 100% result would mean no boarding pass without watching the video again and retesting. Frequent flyers with a given airline could be exempted from watching the video and directed directly to the test, with the same 100% pass mark.
I'd also have an extra test for exit row seating with no retest ability – that is, you fail, you're not in an exit row and that's it.