When a robust, reliable countermeasure for SA Level 3 failures arises, aviation will be a lot safer.
SOPs, ECAM, TCAS, GWPS, and other technological advances have made aviation vastly safer than it was a few decades ago. The only component that cannot be improved is the human mind. While these days it is politically incorrect to state the obvious, humans are NOT born equal. Some have better cognitive abilities than others, and even that can be split into many mental and motorical skillsets that make us up as individuals. I for instance can read very fast, well above average, however my handwriting borders on the illegible even with the greatest attention. Any training program by nature is designed for the average, with a line drawn at some minimum requirements below which the less skilled will fail. However there will always be individuals with marginal performance, and it is always a huge dilemma on where to draw the line. The lesson of the past 50 years is very clear. Rather than trying to improve the human, improve the automation to make the task easier. Of course it has taken all the fun out of the job (for those in the upper skills bracket), but it made, and continues to make things a lot safer.