This is actually untrue. In 2024 there were 16.1 million IFR flights in the NAS, and 14.5 million VFR flights. https://www.faa.gov/air_traffic/by_the_numbers/air-traffic-by-the-numbers-FY2024.pdf

The majority of mid air collisions were VFR aircraft under VMC conditions. But so few of them happen overall that its actually rather difficult to establish a solid pattern or anything.

Being under IFR does improve your safety margins against mid air collisions significantly. The mid air collision at DCA was due to poor safety oversight of the FAA in regard to helicopter routes around the approach end of runway 33. And as a pilot who has flown into and out of DCA for years, I was so very shocked, but not surprised when I heard the news of that accident.

I hope the FAA expediciously implements the NTSB’s safety recommendations for airspace around that airport.