> The stock market is a closed system that currencies feed into

Currencies feed into the stock market, but it's not a closed system. If you think a company is undervalued in the stock market, and you buy shares, that raises the price of shares for that company. With a higher share price, that company can borrow money (by issuing shares) at better terms, and spend that money on growing more than they could have if they had not borrowed that money.

If the stock price is too low, the company may buy back shares of its own stock (thus enabling future borrowing). Alternatively, investors may buy up a majority of the stock of that company, thus acquiring control of that company, and either try to force the company to do a thing they expect to be profitable, or liquidate the assets of the company (which will then be distributed to shareholders in proportion to how many shares they hold).

So basically the stock market moves money to the companies based on how effectively they could spend borrowed money / how valuable they would be if liquidated.

Currency is a tool for measuring economic value, it's not the basis of economic value.

This is why fiat currencies are so useful: you can change the length of the "ruler" to accommodate changes in the thing you're measuring, so the value of the increment remains stable.

No, companies create excess value and grow. Tesla pre Model 3 is a very different company than Tesla post Model 3. A drug company is very different if they've patented a new wonder drug. New companies come into existence and offer shares via an IPO.

Investing in the stock market is literally investing in the collective appreciation of the value of the companies that make up it.

But there's stocks on the other side that represent real things that increase in value. E.g, compare Google 20 years ago with Google today and see if you think it's more valuable.