The reason why a PO can explain something in English, and you get something useful out at the other end (of the developer), is because of a myriad of other decisions you don't see. The reason why some software systems end up being efficient in maintenance and further development, is because of these myriad of other decisions.
The many decisions are the "devil in the details" that LLMs don't get right. Or, let's not anthropomorphize unnecessarily -- LLMs don't know right from wrong, and don't reason or reflect. They could only get this right by sheer luck. In a big numbers game, they'll always get it wrong. If you want to be a PO (or vibe coder, etc) and use English language on one end, and get these details right, there is only one possible approach:
A tight loop with expert knowledge reviewer. The programmer that knows pretty much what they want, in a small section. A LLM can draft it out so that the programmer saves time typing. This isn't really useful for the PO. (PS: The same general advice applies for any other use of LLMs. Tight loop. Expert reviewer)
You'd need a language that can express important details otherwise lost to the English language. And you'd need this to be deterministic. The "myriad of tiny decisions" are the true basis for the code implementation. If they're not expressible in the English language, and they're not achievable by LLMs, there really isn't any other way to achieve them.