It is my biggest problem now: AI is very good at adding things. It does not notice that things can be removed.

This is true for both code and prose. Even when it does notice something wrong, it wont remove it, but keep the sentence and make it longer.

"This is A" -> "This is B, not A"

It makes it incredibly hard to write plans and documents and maintain code.

When I tell it that the file is getting overlong and complex, unless I mention explicitly each single point, it just plainly doesn't see the problems and instead removes important bits. I did not yet find the right wording to express it to AI in an automated way.