A game's 21-inch battleship guns and larger historical proposals

Is a 33-knot game battleship with six 21-inch guns entirely implausible?

The reply points to historical proposals for guns as large as 24 inches, without assessing the game ship's complete design.

The question describes a game battleship with a speed of 33 knots and six 21-inch guns. Historical proposals went as far as 24-inch guns. That comparison addresses the proposed gun calibre without establishing that the game's speed, protection, and armament form a workable ship.