A big airplane style drone isn't hard to stop, but the new wars will use swarm drones.

Like here's a drone that recharges from power lines so it basically has unlimited range and can carry a much heavier payload. You going to shoot down edit: your own power lines?

Of course it's easy to stop this one attack, but there's so many ways small drones can get around defenses. They're like the technology version of asymmetric guerilla warfare.