The counter for drones will be the proliferation of CRAM/CIWS and APS. Currently there exists cheap, publicly available (and commonly heavily open sourced) tech stacks for drones but the same is not the case for CRAM/CIWS and APS. But fundamentally the systems that can effectively kill artillery shells, mortars shells, rockets, and missiles in flight will be able to kill drones as well. There are some differences (such as that drones tend to fly lower/slower) but fundamentally the tech applies the same.
And to be entirely honest this proliferation is almost entirely a software problem. Of course the existence of public hardware designs is important as well but getting effective sensor integration, detection, targeting, tracking, and response at a low enough latency will be bottlenecked by access to high quality domain specific software.