but if you know there are 3 CIWS, you know they can move the pew-pew pipe at some radians per second this axis, and that axis, you put the drones in a formation to maximize the need for muzzle movement, estimate how many rounds are in them (or how long can they fire before getting overheated)
and send that number + 1 drone.
.
.
of course it's a bit oversimplified, but really with decoys, and putting cheap shaped charges on them ... they can fuck up the launch/landing surfaces, the AA capabilities, there's absolutely no way to jam them if they have the "last mile" set to automatic.
(yes, in theory a dumb and big fireball or good old flack can take out a lot of them, seems trivial, but in practice we don't see that, instead we see faster drones trying to intercept them)