yes, llms can produce bad code, they can also produce good code, just like people

Over time, you develop a feel for which human coders tend to be consistently "good" or "bad". And you can eliminate the "bad".

With an LLM, output quality is like a box of chocolates, you never know what you're going to get. It varies based on what you ask and what is in it's training data --- which you have no way to examine in advance.

You can't fire an LLM for producing bad code. If you could, you would have to fire them all because they all do it in an unpredictable manner.