> If it is distinguishable, can’t the machines do the distinguishing?

No? Just like they are not able to reliably tell if a piece of text was LLM written or not aside from by having access to the watermarking that some providers and models intentionally embed in the text.

> If crap is indistinguishable from substance, is it truly crap?

The crap is very very distinguishable. But there is so much of it we have to wade through, and it’s only getting worse.