In my opinion their size is ok. The generator is made with a fantasy setting (and its epic castles) in mind, so generated citadels are larger than average real-world castles, but not unrealistically large. What really bothers me is their design - a single ring wall and a single huge building (a keep?) inside. That's not how most real castles looked, but on the other hand this way they can be very easily identified on a map.
Viewing post in Question regarding scale
Looking at a few on google maps with satellite view, I see two common patterns: the ring wall with centrally isolated keep, and a ring wall with many buildings barnacled on the interior surrounding an open space.
The open space was usually used to marshall troops, or for huddled masses of refugees (e.g. all the rich bastards from city).