Shooting down Drones in the latest NK war would have caused far bigger disruption to the Azeris than actually killing their soldiers. The cost a successful strike is not only the cash burnt from the adversary but also its capability.
Of course I agree, but the problem with drones is underestimation... people hear drone and think cheap simple remote control planes kids make and play with.
After 2008 conflict with Georgia the cry was... why is Russia so backward in drones... they are making 5th gen fighter projects and strategic bombers.... why can't they make cheap simple drones... or diesel engines for corvettes.
The fact of the matter is that drones and diesel engines are easy, but good drones... useful drones are like good engines and efficient engines... you need time and money and experience and if you haven't done any of those three things they they are bloody useless.
NK did not pay attention to air threats... they didn't do enough to hide from airborne cameras, and they also didn't plan and train to go against drones either, so when they were faced with the drones they didn't have the time to develop countermeasures.
Take someone who has never shot at a bird in flight duck shooting and tell them to shoot ducks without instruction and they will be awful.
Worse than that when it is drones that might be carrying bombs, those ducks will attack those ground targets and kill them fairly easily.
The point is that with proper camouflage those ducks wont know the enemy is there, and will fly over unaware they are vulnerable, which creates more opportunity to shoot them down.
You could spend billions on air defence missiles only to find they wont like drones because they don't have enough of an IR signature, or the radio proximity fuse just goes right through a small plastic drone so the missile just blows past these drones without exploding and damaging them.
What they needed was training and planning in dealing with drones and enemy air power (drone or otherwise).
If they are serious they will be working on this now.
Buying thermal sights would be a good start, but jammers and things like your own drones fitted with armoured fronts designed to ram that you manually fly around using a remote so you could fly into enemy drones and knock them out of the sky could be done on the cheap and reused against multiple targets...
But fundamentally buy some drones with cameras and use them over your own positions and see how exposed and obvious you are and start working on camouflage and set up some fake targets for the enemy to waste time attacking too... it does not need to be expensive...