Drone swarms at sea are different from the land kind as there's no terrain to hide behind.

Here's some interesting reading: missile interceptors, at price per shot. "Iron Beam" looks great, at a paltry $3.50/shot. But it's Israeli. We know lobbyist money would prevent the USN deploying it. Instead, Billions would be paid to Raytheon or Lockheed, and decades will pass, with nothing useful ever appearing.

missiledefenseadvocacy.org - Missile interceptors by cost

Best bet for the next layer out from the Phalanx, would be the RIM-116, at $1M/shot. The US "JCs" are already making their money off it, probably because it was developed in the early 90s, before the philosophy of "Billions for development, nothing for deployment" took over. BUT, a quickly reloadable launcher is needed. Right now, a VLS is not reloadable at sea. The RIM-116 mount has 21 cells, but a drone swarm will empty that pretty quickly. The missile is light enough for two big, husky, guys to lift into the mount, but, can they reload fast enough? We need something like the old twin arm mounts, where missiles are brought up from a huge magazine, far below deck, then run out on the launcher in a few seconds, as needed. Maybe something that works like the old mounts, but, instead of loading a single missile on each arm, load a magazine with 4 or 6 missiles, on each arm, with each reload cycle. Keep in mind, it isn't firing off $1M missiles, it's keeping the inbound weapons away from a $13B carrier.

Of course, Stingers have a considerably longer range than a Phalanx, and cost "only" about half a mil, but, apparently have an impact fuse, so would need to effectively "hit a bullet with a bullet", vs the RIM-116, which uses a proximity fuse.

Steve...saw an impressive demonstration of a RIM-24 Tarter mount on USS Columbus in 1963.