It’s not, and in fact it is opposite of truth. The reason, for example, why free market economy works better than centrally planned one, is precisely that obtaining full knowledge is impossible, so it is impossible to effectively centrally plan, whereas in market economy, each individual contributes their own private knowledge that is unavailable to other people, through participating in market and communicating it through price mechanism.
See, for example, Thomas Sowell’s “Knowledge and Decisions”, which is precisely about this point, or for more classic reference, Hayek’s “The Use of Knowledge in Society”. Again, to reiterate, the entire point of market economy is that nobody has full knowledge.
Along with sometimes being smart or hard working, people are also sometimes lazy, dumb, irrational, careless, destructive, and so on. The point being, there is a wide variety and they bring their messy contributions to the market, which makes for a very messy market. There can never be perfect anything. It's not even a good theory, it's garbage, it would only work in a simplistic simulation with no chaos.
Perfection competition theory is incorrect, badly flawed in a similar manner, as the efficient market hypothesis [1].
[1] https://en.wikipedia.org/wiki/Efficient-market_hypothesis
It was being slapped on everything to a)be lazy about not actually having allergens get into food because b)it fooled consumers into thinking that the disclaimer meant they weren't liable for allergens in food.