Why would "pop and drop" be undefendable? It's not as if the ship won't be able to see the ASCM the entire time it's doing that maneuver. The Harpoon does it be

Why would "pop and drop" be undefendable? It's not as if the ship won't be able to see the ASCM the entire time it's doing that maneuver. The Harpoon does it because of it's origin: it was supposed to hit surfaced Soviet submarines, and it needs to do it in order to actually hit the target. But that target class disappeared before it really reached service. ASBMs have a similar issue in that there's no way for them to get out of the radar view of the target (or a ship near the target). And we've got missiles designed to take them out as part of the target set (SM-3 and SM-6 are quite capable, depending on range). Drone subs are just mobile minefields. The idea of a mobile minefield isn't new, and you have all the problems of a minefield (including, but not limited to: sinking ships you didn't intend to), along with new challenges like: how do you communicate with your drone subs? Your cheap anti-air drone is just a missile carrier? You're thinking weapons, not systems here. How do you target with them? And how do you keep them from getting targeted? Even being 20kft up (and improving the range that way), an equivalent AAM from a fighter will have longer range, simply because it's able to be launched from Mach 0.85, instead of 30kts. Sure, the drone might be cheap, but the missile won't be.