Stock markets are operating systems for resource allocation. By this I mean that stock markets are distributed systems comprised of humans and mostly bots. These systems anticipate which ventures will produce value in the future. Generally speaking, they do not generate value themselves, but serve as a medium to communicate information about value. If you know something about a company that others do not, and trade with this information, you will be given a reward for your marginal contribution to the aggregate knowledge of the market.
This is all to say that I largely agree in the notion that stock markets serve a function in society. However, I do not endorse the get-rich-quick schemes that are often associated with it. My personal opinion is that too many intelligent people are misallocated in optimising these systems by fractional amounts to capture value, rather than increasing the net amount of value in the world.