The systems are exposed yes .
But we see the Battlestar as alone depicted in the series or as flag ships.
Look at carriers in the us navy .
they are supported by a whole fleat of destroyers , refuel ships and so on.
Alone a carrier is vulnarable to certain attacks, but with its support vessels a difficult target to hit.
Sadly in the original series we dind get to see that (Afterall it was about the sole surviving battlestar)
Back then budget might have bin at play aswell.
