I’m a big fan of your writing, but on this topic, I believe you are mistaken. We do not, and did not have, an “extreme” version of capitalism. We have monetarism, which is distinctly and explicitly not capitalism.
Capitalism didn’t fail, capitalism was quietly murdered by the elite and replaced with an imposter that serves the interests of the political and financial elite, at harm to everyone else. All blame should lie with the imposter and those responsible for the ruse.
“Mixed economies” aren’t the best, mixed economies are simply the only way for strong social programs to function, because social programs operate at a loss, while capitalism (and monetarism, the dastardly imposter) operates at a profit. Thus you perceive “mixed economies” to be most functional because there isn’t a capitalist economy for comparison, and the for-profit nature of monetarism enables subsidies of the loss-leader aspects of expensive social programs. When the social programs become more expansive than the profits that subsidize them, credit lines are tapped (and exhausted), faith in the currency evaporates, and the government (eventually) fails.
Your use (and the common use) of the term socialism is also a misnomer. Socialism is the ownership of the means of production by the government, which holds in only a few general cases for governance (Venezuela, for instance), and only in a few specific asset classes in “mixed economies” (Norwegian oil, for instance). These “mixed economies” aren’t socialist per se, they just have strong loss-leader social programs.
You aren’t responsible for the inaccuracy of the terms we use, you’re just repeating the inaccuracy from other people’s language. Misunderstanding these terms is rife in our society, and institutions, including the media, have disincentives to explain this to the public. After all, “In a time of deceit, telling the truth is a revolutionary act.”