I think that looking at statistics and studies by international organizations, countries that are democratic and have socialist policies have a higher level of development (which means lower infant mortality, better life expectancy,better level of education), lower inequalities and lower crime rate. So I think having socialist policies in a democracy is very desirable, and that the vast majority of socialist parties are nothing like the Soviet Union.

If you look at economics, you know markets need regulations because of flaws that deviate it from the pure and perfect model, and that the market is not efficient at all in some field where the state needs to either produce it itself or subsidize. The perfect efficiency of completely free markets doesn't even exist in theory, much less in practice