The actually most just is pure Socialism, but as that is impossible to implement for several reasons, Capitalism is the next best choice. It allows for a middle class to exist as well as upper and lower. Socialism in practice results in a very small elite and almost everyone else as lower class. While in Capitalism there is still a lower class, it is far better in Capitalism as it actually possible to reach middle or even upper class. Position in life is not mandated by government, but controlled by you and those around you who are affected in the same way, as in by you and others. Looking at the American system, it is a mix of Socialist and Capitalist ideals and is what makes it so unique. As of the last couple decades, we've become more and more Socialist to try and fix the downfalls of Capitalism, and while still far from perfect, it is better than any other system so far.
Capitalism is the most just economic system as it provides equal opportunities to its followers. It is also more effective as time and again it has been proved. Any other economic systems are skewed in favor of a particular group. This is not so in a capitalist market. We observe every day how more and more economic systems are starting to follow the capitalism. Even a communist country like China has been following this system and another communist country like soviet Russia collapsed. People blame capitalism in the sense that rich becomes richer and poor becomes poorer but in reality Capitalism is the best bet for a poor man to become rich due to many opportunities that it provides.
Capitalism may seem like it gives everyone an equal opportunity to be successful, but not everyone's life experiences offers an equal chance to be successful. For example if one a persons parents could never afford for them to go to school compared to a kid in a rich family whom has enough money for school these two people would never have an equal chance to be successful in a capitalist society
Capitalism is not a just economic system, inequality is rife within capitalism giving the members of the uppers class significantly more power than those of lower the classes which creates unfairness and resentment among the people. Capitalism also allows for the economic exploitation of the poor by the rich. Capitalism is also at least theoretically not the best system, libertarian socialism (socialism with freedom), mutualism (free market anti-capitalism) and Communism (as in actual communism not soviet totalitarianism) are all arguably better than capitalism but capitalists try to marginalize these ideas by buying most the means of mass communication (media) and either ignoring these ideas, or trying to criticize these ideas by conflating them with totalitarian groups that ever truly implemented these ideas and probably never would have and many other shifty techniques so they can continue to amass wealth and power under capitalism.
I am not 100% pro-free market,but capitalism has been shown to be the best Economic system. I believe that the government should have an obligation to provide for those who are not provided for, but having some form of a free market is required in democracy and to improve the well being of all.
Capitalism isn't just, but economics isn't about justice