The basic truth is that the FAA will not accept a collision avoidance system, no matter how good. It would be a threat to their vast ground-based empire. If there were an effective and widely implemented CAS, we could turn off the low altitude system. In busy areas the controller pushes a switch which suppresses all VFR codes. Actually, the system works pretty well in good weather.
Bad weather is the main cause of delays.
When a major airport sustem like New York or Chicago goes down, it affects airports hundreds, even thousands, of miles away. Another problem is the shortage of runways, exacerbated by the airlines' practice of hubbing and spoking. A modern jetport is a multi-billion dollar deal, is noisy and most people don't want to either have it or pay for it. I know this sounds a bit negative, but I've been there, done that for the last thirty years. I really don't know a soul in the present FAA with any authority.