This is sort of circular, the stock market can also devolve is pure speculation and go full casino, which are generally considered an example of a not-necessarily-net-positive addition to society.
it's not circular, but more to the point, you suggesting that the stock market can devolve (fail) is like saying "brakes on a car can fail, so brakes are stupid." Brakes are not stupid.
I did not say that, I said that just because the people working with stock are getting paid does not mean that the stock market is doing something useful. Parassitism also exists in free markets.
Stretching the brake analogy it would be similar to noting that just because you are pressing more your brake pedal it does not mean that your car is slowing down faster, sometimes you need an ABS
the aggregate success thrown off by the stock market is a measure of the usefulness of the stock market.
participating in that is what enables to stock market to provide its usefulness.
so, yes, success on the stock market is a function of usefulness in the real world.