All versions of a 'mixed' economy are failures. Those who criticize capitalism are really criticizing cronyism and fascism (and these are unquestionably failures), not the free market.
Those who claim that the free market has been tried and cannot work 1). don't know theory and 2). have no empirical evidence and 3). ignore the fact that all of the alternatives and every type of interventionism have failed miserably.
The state-of-the art theory of laissez-faire is the divine economy theory. To everyone who doubts whether an unhampered free market can rescue humanity from oppression and injustice and bring about peace and prosperity it is incumbent upon them to do their homework and read about the divine economy theory.