Automatic ballista control.

Then explain to me why not write a program that does everything for you: collects resources and builds Castles?

Such a program has been written (AI)... Have you never played against the computer and seen how the heroes run around, collect everything, and the Castle builds itself? ...;)
In short, it's a computer player... and very often this program is rewritten several times to improve the "behavior" of the AI.

And no one answered my question about casting: why is it forbidden?

Let me answer: have you seen this in the rules of some online tournament? The fact is that most online players consider this technique imbalanced... that is, this technique to some extent prevents players from demonstrating skill rather than luck... by the way, this technique is not prohibited everywhere.

And in general, is this skill? It's just pathetic whining! Yes, I'm a master because I defeated hordes of zombies with one elf, I'm a god of heroes! It's just nonsense.

No one says that this is the pinnacle of skill, but it does relate to the ability to tactically conduct battles... I personally also have a negative attitude towards such battles, although some people use them.