The Fundamental Issue: VFR and IFR are BOTH Obsolete
The Fundamental Issue here is that both VFR and IFR are entirely obsolete. The entire US ATS is based on the long obsolete flawed premise of "see and be seen" related to 91.113(b), which has failed time and time again, from the Grand Canyon midair, to AL853 (Sept '69) to Aeromexico 498 at Cerritos, to PSA182 in San Diego.
Further, seeing hundreds of thousands of new tiny UAVs flying into a sunset, for anybody, from F-16s to B777s, to even low end GA, is virtually hopeless. We now can economically and safely do EFR (Electronic Flight Rules) globally, but IF AND ONLY IF WE reformulate ATS from first principles, use dynamic RNP 3D and 4D trajectory based separation, exchange the correct "state vector" data, (and NOT FAA's ridiculous overspecified overexpensive seriously flawed version of ADS-B with UAT and ADS-R), and finally do C-N-S properly (but NOT NextGen, which really should be called PastGen).
This event isn't the F-16 pilot's fault, it isn't the C150 pilot's fault, it isn't the Air Traffic Separation specialist's fault (I feel bad for all of them, and they all deserve our sympathy and support).
Instead, IT IS primarily the FAA's FAULT, and our fault, for completely failing to force the needed ATS evolution over the past 4 decades, and OUR failing to hold FAA adequately accountable for sustaining this broken, antiquated, seriously flawed system, that will someday see this sad event again repeated if we don't now take action. FAA needs to be broken up this fall in the budget hearings, and re-constituted with a completely separate ATS that is PROPERLY modernized, and much more closely held accountable for its design, costs, benefits, and performance, ...directly to the airspace users, and NOT to FAA's contractors, consultants, avionics companies trying to economically benefit from mandates, and politically appointed or career FAA officials with marginal or no serious aviation experience.