>> In a world where apparently drone-swarms are this cheap...what, no one ever developed counter-drones?

Well, in a world where developing assault rifles is actually rather cheap, nobody has really developed any convincing countermeasures. Infantry still gets killed if you shoot them with an AK-47, etc.

So there can be weapons without countermeasures. The point of the video is that the possibility exists to develop the weapon to begin with - and that is already concerning enough.