Modern US and NATO armor/vehicles have air conditioning (and aren’t crammed full of stolen loot… before a battle). Just closing the hatch goes a LONG way towards limiting the effectiveness of a DJI with a hand grenade taped to it. Same with actually setting up the overhead cover to protect from mortar fire at night rather than just leaving said tanks to air out.

As for larger targets and installations? Most modern militaries (all EU/NATO?) have early warning systems that are effectively a microphone array used to pinpont where gunfire is coming from. Whether they are installed on ships/bases, taped to the back of a vehicle, or literally worn by infantry.

And drone engines tend to be pretty distinct noises. They might not come up until it is too late if you are having a conversation with your buddies but if you have a simple filter listening for them… Which is existing tech in place at airports and even the better funded public events.

At which point it becomes a much simpler version of the problem of shooting down ballistic missiles. Think stuff like the Phalanx which is basically a computer attached to a minigun with the human in the loop theoretically agreeing to fire.

Modern drones are very much along the same level of danger as mortars. If you are close enough to deploy one, you can cause some real chaos. But a competent military can minimize the threat considerably.

And… much like mortars, the real threat is against civilian targets where you might not have a machine gun or two controlled by a few microphones and a gimbal… yet. The world is real fucked so give it a few years until that is the norm in a lot of countries.