The problem with drones is that they can be very small, and very cheap.
The first part makes them difficult to detect and target. The second part makes destroying them with, say, guided missiles, extremely inefficient. You can basically bankrupt your opponent by sending more drones then they have missiles to shoot them down with.
Creating hard counters to modern drones is going to require radical new thinking. I suspect energy weapons may end up playing a serious role in this regard.