I think you are coming close to a 'no true scotsman' fallacy here. Varying degrees of collective ownership of the means of production have allowed a great many countries to increase standards of living, and general welfare. Of course if you dismiss the peaceful and thriving democratic socialist states as impure, you are left with more authoritarian and communist ones. But then in order to make a fair comparison, you would have to dismiss the 'impure'ly capitalist ones. Like the US since even before the New Deal. Is there a purely capitalist state even? Because by your logic if pure capitalism were so beneficial, many countries would be doing it.
I think rather, it is the power-hungry dictator part that is problematic like all centralized power. As they say, it corrupts absolutely. This is true whether in the form of communist bureaucracy, non-substantive democracy, nationalist demagoguery, or the disproportionate influence of the bourgeoisie in capitalist systems. For me, the key is self-determination - the better system is the one that affords individuals greater opportunity to pursue their chosen destiny. Socialist democracies with decentralized power structures do a very good job of that IMO, certainly better than communism or pure capitalism.
PS some of your arguments sound like you might be confusing socialism with not only communism but also state capitalism, where a (usually authoritarian) government directly controls capital and production as opposed to the workers as represented by the state.