People like to view the problem as a paradox - can an all powerful God create a rock they cannot lift? - but I feel that's too generous, it's more marking your own homework.

If a system can both write text, and detect whether it or another system wrote that text, then "all" it needs to do is change that text to be outside of the bounds of detection. That is to say, it just needs to convince itself.

I'm not wanting to imply that that is easy, because it isn't, but it's a very different thing to convincing someone else, especially a human, that understands the topic.

There is also a false narrative involved here, that we need an AI to detect AI which again serves as a marketing benefit to OpenAI.

We don't, because they aren't that good, at least, not yet anyway.