It’s the only system that relies on the willingness of two parties to exchange something of value in a way that it mutually beneficial. Every other system involves the use of force, either explicit or implicit to compel people to act in ways that are contrary to their own interests. Because if it were in their best interest, force wouldn’t be necessary. Capitalism requires a willing buyer and a willing seller. It’s the most free system there is. Inefficiencies obviously can create problems, but in those problems, there are yet infinite possibilities.