I think this is a huge misconception and I don't think it works this way. have you heard people say 50 is the new 40, etc.? The same thing would work at older ages. Sure the last 10 years are a decline, but you are pushing those years out not adding more of them.
Yeah makes sense, if you already have metal ships carrying goods there is no need to make additional ships just for protection. I suppose there could be an economic advantage if the pykrete ships can be made significantly cheaper and faster than the cargo ships.
It makes me wonder why Ukraine is so successful in the black sea with their sea drones vs. the Russian navy? Why wouldn't Russia have ships or something else blocking their battleships at port? It seems Ukraine is able to sink everything with ease at the moment.
What if, instead of building a full carrier out of pykrete, you instead build very simple pykrete ships that follow around the outside of a carrier group to add a layer of protection from torpedoes and sea drones?