As pointed out by the ATSB, this is the first ever midair between IFR aircraft OCTA. The first ever. And communications overload is the obvious reason. And that has been caused by the CTAF/ATC interaction. And that was brought about by? I don't see anybody suggesting traffic lights at every intersection.
Traffic lights are a good example, you can install them, and still there is fatal accidents because somebody runs the red signal and the crossing traffic on green assumes its clear so is not looking for a conflict. Interesting that roundabouts don't stop collisions but they lower the severity of injuries compared to traffic lights as the vehicles are forced to slow and look. Any mistakes are confined to lower speed accidents vs red light accidents where the offender has no physical barrier to make them slow down.
Point is if you think something else is doing the job for you you tend to be less cautious about the unexpected.
I mean they had to physically employ raised barriers at some rail intersections as cars just continued to hit trains, so they basically said stuff the driver, here's a big wall to stop you ramming our trains. Or just spend billions building tunnels and bridges so cars don't interact with the trains at all.