You knew exactly what you wanted, since you already built it. All decisions were already made, all tradeoffs reached. LLMs are definitely helpful, but try exploring something new with them and you'll slow down significantly.
It happened fast, as you prompted it just the right way. Another person, who doesn't have all that context in the mind, would fail quickly.
For example I have decades of Software experience, but wont know where to even begin what OP did.
It’s kinda the old saying about $900/hr expert that only taps with an hammer. The price is not about tapping, it’s about knowing where to tap.
Simple, you start by asking LLM for more info.
But this has always been a developer's work, it's understanding what is needed, translating it to working software, and judging the result, and doing so at scale, over time, and with other people.