The alternative is the traffic control model we use on roads that actually scales up. Cars can go wherever they want and whenever they want as long as they don't enter prohibited areas, remain under certain velocity and don't collide with each other. I think this would be perfect model for drones. We can have two types of drones: (1) which are equipped with level of tech that can do obstacle avoidance and have restrictions map (2) all other. The category 2 should fly below certain altitude and weigh below certain limit. Category 1 should be able fly anywhere as allowed by restrictions map. There is no need for centralized air traffic control.
So, so many people trying to solve this problem. This is just the flavor of the month.
The FAA has not mandated that on “all aircraft”, only on those aircraft seeking to use airspace where transponders are currently required. A lot of aircraft will choose not to equip and remain perfectly legal to fly.