I wasn't saying that battleships are a good strategic choice to develop, just that you can't "easily calculate why its impossible to build a battleship beyond a certain size".
It is possible, it's just not strategically advantageous.
Just like throwing more compute at a neutral network isn't going to make general AI. The diminishing returns comes with how brittle their learning and representations are.
This is not true. The biggest battleship bought was the yamato
> Length: > 256 m (839 ft 11 in) (waterline) > 263 m (862 ft 10 in) (overall)
The biggest CV (aircraft carrier) right now should be the Nimitz class with
>Length: > 317m
which seems to emphasize your statement, but, battleships are not versatile and battleship development pretty much stopped after WWII. The germans had propsals of the H-class battleship, with a total length of the H-44 of 345m.