Really? I find LLMs quite bad at deleting code. If you ask them to add a feature, then later take it out again, the codebase still grows. It always grows. Every time I've tried it, llms have failed to simplify code via refactoring. Even fable is incredibly bad at this for some reason.

LLMs are excellent at making prototypes though. And prototypes can be an excellent way to stop yourself from implementing the wrong features in the first place.