Author is arguing:

* LLMs, when presented with a question to which they don't know the answer, tend to make up a wrong answer rather than say they don't know.

* Therefore, LLMs are useless.

Yes, LLMs do that, and it is a problem.

No, that does not make them useless. It's usually much easier to check their answer than it would have been to search for an answer yourself. If they are right, you saved time. If they are wrong, at worst you wasted a couple minutes. But they are right often enough that it can be worthwhile, especially if you have a feel for what questions they are likely to know the answer to and what questions they aren't.