To continue the carpenter analogy, the issue with LLMs is that the shelf looks great but is structurally unsound. That it looks good on surface inspection makes it harder to tell that the person making it had no idea what they're doing.
Very good analogy I'd say.
Also similar to what Temu, Wish, and other similar sites offer. Picture and specs might look good but it will likely be disappointing in the end.
Regardless, if a carpenter is not validating their work before selling it, it's the same as if a researcher doesn't validate their citations before publishing. Neither of them have any excuses, and one isn't harder to detect than the other. It's just straight up laziness regardless.