imagine a society where genuinely good outcomes (good health, good prospects, stability) occur without outside intervention!

Many religious people believe that there is some overall intelligence (God) guiding everything and preventing us from fucking the world up.

Other people believe that the world would be perfectly regulating itself if only humans would stop interfering and go back to living as the other great apes.

We see self regulating systems around us in nature and think that is the rule for how the works. But it isn't. It is survivor bias.

We see self-regulating systems because they tend to last longer than systems that don't or can't self regulate - and because we have a fundamental tendency to see patterns in order to try to predict what is coming next.

The most damning thing about the "self-regulating market" idea is not that part though. It is the assumption that something self-regulating would inherently be more desirable.

Pushing a system outside the inherently stable region is the basis of some of the most efficient systems in engineering. Your phone charger is a tiny thing that can fit in the plug on the wall because it uses dynamic switched mode regulators to transform high voltage AC to low voltage DC. You can make an inherently stable system that does the same by using transformers, but it would be much more costly, weigh much more and would often be less effective.

But even that would be something we specifically designed to be self-regulating.

A self-regulating market can exist, but it may easily self-regulate to a level where everybody is starving. If we want a better outcome we need to regulate it. That regulation method can be something that works without constant outside intervention, but then it is also likely to be less efficient and everybody is likely to be worse off.