Capitalism hasn't existed forever, it literally started in the late 1700s during a period called The Industrial revolution, when factory machining started the first cottage industries that pushed out previous modes of hand crafting.
At that point, when machines and cottages to hold them started to be required for mass production and hence competition in the market (pushing out hand crafting as a competitor) CAPITAL became a requirement of mass wealth accumulation... because one needed large sums of Capital to buy the machinery, rent the building, and hire and train the workers to exploit. So it became the limited province of the already well off to do.
That's when Capitalism was born, and why it's named CAPITAL-ism. Because it has Capital requirements if you want to join the Capitalist class. It was created in the British Industrial Revolution.
That you're unaware of this change in the mode of production and what it represents, and believe that "oh Capital has just existed forever" is what some Marxists refer to as being in a state of "false consciousness".
The system wasn't always this way, and doesn't have to necessarily be this way (eg. Marx offered the model of workers owning the machinery or "means of production" as his alternative, and there are likely others). Capitalism is a product of a technological "change of epoch" of the "mode of production."
...and it's defined the age we live in, and how we think. Which is what the later Frankfurt School neo-marxists discuss.
P.S. It's also worth noting that the British Industrial Revolution, The French Revolution, and the American Revolution all overlap in time periods. Live was very different before the late 1700s.