The idea of lemonade-stand capitalism suits their ideology perfectly — but it is a myth. In reality, the more “free” a market becomes, the more the competition gets rigged. In a capitalist system, the main goal is to grow and accumulate indefinitely.
Competition is an effective way to drive innovation and efficiency in theory. But as businesses grow into large corporations and gain larger shares of the market, smaller producers can no longer compete, and must either work for the competition or exit the industry. We see this dynamic at work in the dominance of companies like Walmart and Amazon, who have managed to stack the deck overwhelmingly in their own favor and drive innumerable smaller competitors out of business.
One thing about capitalism that free-market libertarians do not seem to understand is that it represents a constantly evolving social system.
This also means that theories must also keep up with reality, and not reside in past centuries. In today’s world, corporations rule, and in America, as regulations have become laxer over the past few decades, they have grown even larger, especially in the finance industry, where the biggest corporations began merging after the repeal of the Glass-Steagall Act into the too-big-to-fail behemoth’s that persist even today.