The interminable Internet battles over the details of politics are bound to fail when words don’t have the same meaning to all participants. Let’s go over the definitions:
Capitalism: A private individual has a surplus of tools. She lets others use those tools and pays them for the work they perform. The person hiring gets paid by the end customers. Example: a chef hires kitchen staff to prep ingredients with provided tools. That’s how any work gets done efficiently.
Communism: private individuals are prohibited from hiring others, but the state does much the same. In practice, this is significantly less efficient. In order to retain workers, they are effectively enslaved through a prohibition on emigration.
Socialism and its variations, like fascism (by its own definition): private individuals put up the funds and the know-how for business, but government directs the work to various degrees. Doesn’t work well in the long run either, since the individuals are risking their resources without having full control over the process.
What a lot of the US leftists want isn’t communism. They think that they want socialism. Even more than socialism, they want a welfare state. A welfare state can be largely capitalist, so long as a significant part of the proceeds is taken away through taxation. That doesn’t work well either, for two reasons. One, businesses become less competitive compared to their less taxed counterparts. Two, the welfare payments reduce the availability of workers, especially at the entry level. Without entry-level experience, fewer people are fit to work at higher levels, so the overall quality and quantity of producers relative to leeches decline.
Another feature of the welfare state is its tendency to meddle deeply in personal lives, using withholding of payments or benefits to modify behavior. Its proponents view it as a plus, thinking that their personal biases would get enforced for them. They are in for a disappointment.