Has anything changed? Governments are hoarding undisclosed vulnerabilities, using them as they see fit instead of fixing. Every espionage, surveillance, or war campaign (see Russia v Ukraine, US/Israel v Iran etc) is followed by a ton of burned 0-days.

>This kind of thing works when you have a significant lead in the field

No? It works even if the adversary has the same capabilities. It only stops working when everything is fixed.