All castles in Heroes 3.

Of course, it needs to be reworked. But agree, the set of secondary skills in Heroes of Might and Magic III is quite simple.

In chess, there are 6 units and no secondary skills at all, yet the game exists without any rework and is still popular. If you compare it to Heroes of Might and Magic II, there will be more skills in Heroes of Might and Magic III, but Heroes of Might and Magic II has not lost its popularity either.
The skill system in Heroes of Might and Magic III is very well thought out for this game. When they created In the Wake of Gods with its expansions, it turned out to be a mess. In Heroes of Might and Magic IV, the skill system is completely different, more complex, but also very well thought out. There is no need to create something that is already bad.