I think you misunderstood.
What we're discussing is whether a set of heuristics to determine whether something is the output of a human or an LLM are "stupid", not whether we should put LLMs in charge of critical work. It's not the LLMs we're talking about, but the heuristics to detect them.
The person you initially replied to claimed the heuristics (to detect LLMs) are not stupid if they are shown to work (by detecting LLMs). The person they were replying to claimed such heuristics were useless.