If there were any kind of comparable Cruiser role ship in FS, I would agree with you. However, neither Cruisers nor Battleships are a good fit, since Carriers are more frequently command ships for battlegroups. As it is, Destroyers are armed too heavily to be classified simply carriers, but are not quite heavily armed enough compared to BIG ships to be called Battleships/Dreadnaughts (which really are the same thing. The HMS Dreadnaught, which lent its name to the class, was in actuality a battlecruiser, known as battleships over on this side of the pond.) Therefore, they fit most comfortably in the role of cruiser, that is, being the muscle, but not being as big as the really big ships, which are arguably Juggernauts (aka Dreadnaughts). The designation of cruiser actually makes more sense when you look at the label of Superdestroyer. Seeing as Heavy Cruisers are just bigger, heavier cruisers, Superdestroyers are just bigger, heavier destroyers. The parallel still exists.