By that logic, we should still live under monarchies today.

Well put, but at that point is it even surplus value? Loosely speaking, if they perform necessary labor in the supply chain, and they’re paid a fair rate (money to live on, not get rich on), wouldn’t their wage count as part of the cost of production?

Modern capitalist economies are already massively centralized and planned – see “The People’s Republic of Walmart.”

Socialist countries fail because they are embargoed, which stifles their economy, which then stifles their legitimacy.

Capitalism is defined by private ownership of businesses.

A socialist business isn’t controlled by a private owner (or major shareholders), it’s controlled by its workers or by the government (or a mix of both). No one sits at the top and gets to award themself a massive chunk of the revenue just because their name is on the deed, so to speak. That’s the difference.