True, but you can't fight a massively distributed attack using a very small concentrated force of professional soldiers; hence the population needs to be issued with weapons and training in an emergency for civil defense. Conventional weapons like tanks and fixed emplacements just become easy targets.

Well then maybe that, too, is a problem that needs solved?

Regardless, a slamfire shotgun only requires two pipes and a nail. Ammo is still an issue, but it's a start.

Why go through the trouble of using drone, just use a barrage conventional missiles, hypothetical country is unlikely to have anti-rocket system like iron dome

IF that's the goal, a Neutron Bomb[1] would be far more efficient. From Wikipedia: "Lawrence Livermore National Laboratory director Harold Brown and Soviet General Secretary Leonid Brezhnev both described neutron bombs as a "capitalist bomb", because it was designed to destroy people while preserving property."

[1] https://en.wikipedia.org/wiki/Neutron_bomb