Sure, I can tell it not to do that, but it doesn't know what that is. It's a je ne sais quoi.
I can't teach it taste.
Recent Claude will just look at your code and copy what you've been doing, mostly, in an existing codebase - without being asked. In a new codebase, you can just ask it to "be conscice, keep it simple" or something.
The trick isn’t to tell it what not to do, it’s to tell it what to do. And give it examples and requirements.