I get the sense that this is a "the world is unfair; there's no way I can succeed" question, so let's back up a few steps.
Income is the starting point to all of this. That could be a job (or jobs), or running your own business.
From there, you can do four things with your income:
- Spend it
- Save it
- Give it
- Invest it
Obviously Spend and Give do not provide a monetary return - they give a return in other ways, such as quality of life, helping others, etc.
Save gives you reserves for future expenses, but it does not provide growth.
So that just leaves Invest. You seem to be focused on stock market investments, which you are right, take a very long time to grow, although you can get returns of up to 12% depending on how much volatility you're willing to absorb.
But there are other ways to invest. You can invest in yourself by getting a degree or other training to improve your income. You can invest by starting a business, which can dramatically increase your income (in fact, this is the most common path to "millionaire" in the US, and probably in other free markets). You can invest by growing your own existing business. You can invest in someone else's business. You can invest in real estate, that can provide both value appreciation and rental income.
So yes, "investment" is a key aspect of wealth building, but it is not limited to just stock market investment.
You can also look at reducing expenses in order to have more money to invest.
Also keep in mind that investment with higher returns come with higher risk (both in terms of volatility and risk of complete loss), and that borrowing money to invest is almost always unwise, since the interest paid directly reduces the return without reducing the risk.