In my opinion, saying that it was a lack of radio calls, and that NORDO should now be illegal, and everyone should be required to have ADSB is silly. If those things prevented mid-airs, why are most mid-airs between planes with radios and ADSB? The plane I rent at the moment has ADSB, but I don't have enough eyes to stare at the screen to find airplanes while I am in the traffic pattern. I don't think most people do. I always make radio calls, but if you've ever flown where multiple airports share the same frequency, you know that half of them end up stepped on, and half of the ones you hear are wrong or leave out important info, like which airport they're at.
Does anyone know where the planes were in relation to the sun at the time? I was flying about a week ago, and I knew there were two other planes in the pattern ahead of me when I turned downwind, but I couldn't see either until they were on short final because of the sun's position.