You are right, Star Fort obsoletes Castle; the problem is that in the city screen appears disabled buildings that can never be constructed, because they can be built on Star Fort, only on Castle, if I am not wrong.
I apologize if English isn't your primary language, but I am having a very difficult time figuring out what you are trying to say here. I've corrected your spelling in the quote to what I think you were trying to say. However, this is still confusing, primarily the bit I underlined.
To the best of my knowledge, those buildings require having a Castle in the city to be able to build them, so them being disabled would be normal. You seem to be thinking it's not normal. Have you tried building the Star Fort? Once you build the Star Fort, can you then build the other buildings?
If the Tech that unlocks Star Fort obsoletes Castle, then you will not be able to build a Castle. Also, you would not be able to build any building that depends on having a Castle in any cities that did not already have one. This is normal and intended behavior. When something has been made obsolete by a Tech, it can no longer be built.
I think he's saying that all the buildings dependent on a castle still show up in the city build screen, even though they can never be built because the castle is obsolete.
According to the Sevopedia, a Castle allows the following buildings/wonders: Himeji Samurai Castle, Castle Garden, Moat, Balistraria, Ballista Turret, Catacombs, Castle Gatehouse, Castle Keep, Herbalist, Dungeon, and Citadel.
The Castle is actually made obsolete by the Economics tech. Economics makes the following obsolete: Castle, Petra, Moat, Balistraria, Ballista Turret, Catacombs, Castle Gatehouse, Castle Keep, Herbalist, Dungeon, and Citadel.
Star Fort is actually opened up by Metallurgy. Star Fort replaces Castle.
I apologize for not actually checking this earlier, but it does seem that all of the Castle's supported buildings get obsoleted at the same time as the Castle itself. If this is not actually the case, then the Sevopedia needs to be updated.
@DH: Were you just interpreting what he was trying to say, or were you actually stating how it currently works? I can't quite tell, and the Sevopedia is contradicting you if the latter.
In that case the appropriate change seems to be making the subsidiary buildings require castle OR star fort I would say.
That's right, and also make C2C show (disabled or not), the buildings I am or will be able to contruct; not impossible ones.