Steep Turns (I believe they are called "Advanced" Turns now!) are in the PPL Syllabus but Emergency Avoiding Action turns are not. The latter are trained in the UK military and, as I have said on other threads previously, I think they should be included in the PPL syllabus.
I honestly do not think we will ever completely eliminate the risk of a midair collision. When I trained at Hamble in 1969 two cadets were killed in a midair in the circuit (one joining and another already in). I also recall a Varsity (I think) in the Cambridge area colliding with a Cessna 150 in the Cambridge area in the early 1960s.
Of course visibility is a factor but like many accidents I suspect the Swiss Cheese model will prevail - when all the holes line up you get an accident - its never down to one thing only.
RIP and condolences to all who know those who tragically died.