I don't believe that Wall Street is well-intentioned in 99.5% of its actions, but still Wall Street creates capital for business: when a company goes through its motions to file and launch an IPO, the banks are the ones who commit to finding X investor dollars. It's easy to ignore the difficulties of that process, given the glut of VC firms champing at the bit to flood the next startup with cash, but it still plays a role.
The difference between Wall Street today and a century ago is the availability of capital. A century ago capital was much more scarce and was mostly held by wealthy private (mostly European) individuals. The stock market was one of the few ways for American companies connect with those people and fund expansion.
Capital is anything but scarce today. Where a century ago the vast majority of people bought savings bonds, if they were wealthy enough to save anything, today the majority of adults need to own stock to fund their retirement. (Itself a novel concept) In addition, vast amounts of capital are held by private equity groups, pension funds, sovereign wealth funds, etc - all chasing the few opportunities for outsized returns.
At some point we reached an inflection point where the need of capital to obtain a return exceeded the demand for capital. Since then the overriding goal of the financial industry has been to obtain those returns by taking them from another player. The original function of providing capital for corporate expansion is almost irrelevant.
