There are other ways to make returns. Return from stock comes mainly from increasing stock prices and from dividends. But fundamentally, it comes from profits.
> Stock prices increase when earnings of the company grow.
There are many reasons stock prices increase. But whether it does or doesn't isn't really relevant.
When a company makes a profit, either:
* the profit is reinvested, the value of the company grows and the stock price grows, making a return for the passive investor
* the profit is returned as dividends, making the passive investor a return as well.
No growth needed for the individual companies either. As long as they are profitable, they make a steady return for the passive investor.
Thought experiment: imagine a company which is going to make 1 dollar of profit per year for all eternity, which it returns as dividends. For an investor with a discount rate of 95%, that company is worth 20 dollars. Say he buys the company for 20 dollars. After 10 years, that company is still worth 20 dollars, as eternity is still eternity, but the passive investor owning the company has made 10 dollars from the company.
As you can see, the passive investor made a return, despite the company only being profitable, but not growing nor shrinking.
You will make a return on your investment when your investment makes a profit, that is capitalism. Whether the profit is increasing, decreasing, flat or going in circles does not really matter, as long as it is a profit and not a loss.