But how do you think new castles should appear?

You seem to be playing the game, and yet you're complaining.

They could have included Inferno as a transition option in the game (especially in HotA), and the Skeleton Converter without requiring a Fortress. They could also reduce the cost of the Treasury and the Stream in the Rampart. It would be good to reduce the armor reduction of creatures from 80 to 60, for example. The Grail could be reduced from 5 to 2500, for example. Increasing the initial growth rate of creatures from levels 1-6 by 50% would be a good idea.