My personally anecdote on poor LLM usage making things take longer:

I had a side (still work) project I wanted to complete that was extremely simple. In my AWS account create an EC2 image builder pipeline that set up a specific component. Just one, very uncomplicated and documented component.

I figured I’d just have Codex do it. I realized after about 3 days of various back and forth in between other work things that we were somehow stuck.

I figured this must be more complicated than I had imagined so I take a look. No, apparently Codex had failed, made an incorrect assumption as to why it failed (again, documents were provided and dead simple) and then continued trying to fix the issue based on the incorrect assumption.