There is no moment when you will feel ready. The skills, the funding, the perfect plan never all arrive at once. Waiting is a way of never starting.
The builders who get somewhere start before they are ready and learn in public. The product teaches them what the plan never could.
Premature is usually just early enough.
Learning in Public
Shipping something imperfect generates information no amount of preparation can.
The cost of a rough first version is small. The cost of a perfect version that never ships is everything.