In the end, I tend to conclude that the socialist economic model, while perhaps a nice idea, is simply too idealistic and therefore unsuited to a world such as ours, where people are fundamentally self-serving. In human society, you will always have to brutally enforce a largely 'egalitarian' system. As a general rule, when you have to brutally force people to accept something, you know you're on the wrong track. It seems that the Western 'elite' know this and know that they have to manipulate people via their base emotions of fear - to get them to accept what would otherwise be unacceptable to them - and greed - to gain control over them by corrupting them (ponerization). That said, I still admire the Venezuelan leaders and people that attempted to implement Bolivarian socialism, even if I think they are hopelessly naive.
Yes, except that I don't know about the general "selfishness" of people. That's kind of the assumption behind both capitalism and socialism and perhaps has its origins in the enlightenment and its simplistic assertion that priests and kings are all selfish. But if you want to deny that priests/kings can ever be genuine and non-selfish, you soon must postulate that everyone is selfish. Along came socialism with its "class warfare" that contains the same idea of universal selfishness etc.
Thing is, capitalists can be unselfish (to the degree this is possible for humans) as well, and often are. I'm not talking about pseudo-philantropic billionaires (though that can be genuine as well), but about all those SME owners who feel responsible for their employees and who work extremely hard. In fact, part of why capitalism works is because people are not all selfish, especially in their immediate environment. And part of the reason socialism doesn't work is that people are more selfish towards a mega-beaurocracy than they are towards their colleagues, bosses and business partners on a local level.
The main reason though why socialism, as a general rule, doesn't work well (I think) is because of the merciless rule of unintended consequences. If you try to fix stuff through a mega-beaurocracy, you would need to be able to "calculate history" precisely, which, of course, is what Marxists do believe. But this always goes spectacularly wrong. I think you can change laws and policies for the benefit of the people on a small scale (small changes and/or very local changes) and with robust feedback, you might make the situation slightly better, which is all you can hope for really. But imposing grand-scale socialist policies tends to completely screw up incentive structures and invites selfish behavior both by workers and capitalists (ironically).
What I hate though about this debate is that people tend to screw up their definitions because of ideologies. For example, privatizing state-owned corporations, having the state retain 50% of the shares but adding a clique of private owners who plunder the whole thing while the state pays the bills (but has nothing to say) has nothing whatsoever to do with free, local markets, but everything to do with greedy theft by a bunch of thugs. FWIW