I guess the only solution then is to already have people in places where it counts. I would suspect military bases have more than enough people. But then again the drones can just fly too high, at which point it becomes a cost/benefit tradeoff, or futuristic laser weapons.

Anything involving people on the ground is just too slow.

It takes radars, interceptor drones, sensor networks, etc. Stuff like this is in active development but not widely deployed yet.