> The best way is, as you say, to have knowledge and skill to create a useful product.

Sure. Once you've actually created a product that's useful, or at least impressive from a technical and/or design perspective, then you're easily employable at that point. But for most people there is still going to be a several year gap between when they start focusing on acquiring those skills and when they've actually built something impressive enough to function as its own signal.

I have seen this over and over with people that have eventually built incredible products or services. The company/product/service etc. can work as a signal eventually. An “entrepreneur” is a lot like a scientific researcher. It isn’t until after the experiment has been shown to work that your risk is then rewarded. The people with high agency that have a fair amount of confidence in their abilities and don’t view themselves as a statistic tend to be able to weather this period the best emotionally.