Which warship was built at the worst time for its own usefulness?
Short answerThe strongest candidates are the Danton class, the K-class fleet submarines, and HMS Vanguard, while Blucher was a sound armoured cruiser harmed by the role assigned to her.
NotesThe late French Danton-class pre-dreadnoughts are an obvious example because they were laid down after HMS Dreadnought had already changed the capital-ship standard. The British K-class fleet submarines represent a concept that naval officers could imagine before propulsion, control, and safety technology could make it practical. Blucher was a capable armoured cruiser but became vulnerable when employed as though she were a true battlecruiser. HMS Vanguard offers a different form of bad timing: she entered service after the war, just as defence cuts and faith in nuclear weapons made a new battleship politically difficult to justify.