The sinking of the Moskva is better understood as a WWII-era lesson - if a warship has lots of munitions up top, unprotected by armor, then all an enemy needs to do is set the first few of those off. Even with an elite crew and ship full of damage control equipment, the ship may end up not worth repairing.

Example: Two 550 lbs. bombs came very close to sinking the USS Franklin - https://en.wikipedia.org/wiki/USS_Franklin_(CV-13)#19_March_... The Franklin was about 3 times the size of the Moskva.

Cheap in comparison to the vessels they attacked.

In Ukraine the Russians had to move the fleet out of Sevastopol because of Ukrainian naval drone attacks, mostly to Novorossiysk and then recently have had to block that in with barges dropped across the entrance to try to prevent underwater drones getting in like the one that damaged a sub there last week.

The recent drone attack on the oil tanker Qendil in the Med was an interesting new one. 2000 km from Ukraine and they seem to have used drones to drop grenades or similar on the ship.