I don't think LLMs need to be able to genuinely fulfill the duties of a job to replace the human. Think call center workers and insurance reviewers where the point is to meet metrics without regard for the quality of the work performed. The main thing separating those jobs from say, HR (or even programmers) is how much the company cares about the quality of the work. It's not hard to imagine a situation where misguided people try to replace large numbers of federal employees with LLMs, as an entirely hypothetical example.