A regulation that mandates, e.g. catalytic converters, creates demand for them. Requiring car insurance, same. Examples abound.
> The Fed also doesn't create demand for products and services.
The Fed(eral reserve) sets monetary policy. It's supply side. By setting interest rates low, it increases demand for credit.
Also, Y Combinator is not popular because it is successful, it is successful because it is popular.
It's no coincidence that Y Combinator operates the most popular technology news link aggregator in the world which all the big corporate tech executives read. This significantly affects the odds of success for startups which join Y Combinator. They choose who wins and it doesn't matter who they choose. If you are selected into YC, it's like winning the lottery.
They should do an experiment; filter out all the obvious scam applications then for all remaining applications (tens of thousands of them probably) run a random number generator to select startups based on keywords that YC likes. I bet the success rate for that batch wouldn't be very different from previous batches.
The Fed also doesn't create demand for products and services. That demand is there, all the time. Right now there is latent demand in the marketplace to extend the human lifespan to 1000 years if possible. There's demand to travel at the speed of light or faster. Whether or not these things are even possible is completely independent of the demand for them.
It's also quite absurd that on the tail end of a decade of a start up boom in the tech industry that you would assert that all these factors make it impossible to succeed today. We are on Hacker News, a site powered by YCombinator, an incubator and investor that has helped make it possible for hundreds of companies to succeed that you claim is impossible. The combined valuation of the top YC companies was over $155 billion as of October, 2019. None of these companies existed 15 years ago.