The hard part is actually deciding and describing what the backend should do. How should it work? What decisions should it make? What's the business logic it has to follow?

You'd want to describe that in an unambiguous way, so you'd have to invent a very strict syntax so that ChatGPT has no way of misunderstanding your intentions. You'd end up with a programming language eventually - just adding more complexity on your way, but you'd end up with code.

Now if you feel that writing boilerplate backend code is tedious, repetitive and verbose and could be automated, I totally agree. Any tool that makes that easier is welcome. But then a language model is the wrong tool for the job, we need more tools like PostgREST, ReTool, and Zapier to not end up writing too much unnecessary boilerplate code.