A formal degree and algorithmic problem-solving is the answer. Always has been.
Have you ever handled a surgical scalpel? It’s an incredible tool - small, light and sharper than anything of its size and purpose. It takes thousands of hours of practice before someone is authorized to use it on human skin, and mastering it takes a lifetime.
You don’t want to give this tool to the wrong person. No matter how motivated, open to learning, well-meaning and hard-working they are, they will mess things up. They might be a chef, a hairdresser or any other professional handler of a cutting tool. Despite their adjacent experience, they will mess up. Handling a scalpel for the purpose of surgery is a difficult job with high responsibility.