You mention Venezuela, but what about India? France, Sweden, Belgium, Canada, Finland, and Denmark are all arguably socialist -- certain much more so than the US.
Any economic system fails when practiced by corrupt or incompetent governments. There are many failed capitalist states, too.
Edit: if you want to talk about scaling, China and India are debatably doing well (or at least improving rapidly), and both countries have 1.3B people.
China had an interesting idea with special economic zones: let people opt out of socialism if they want to, but stay within the country and get basic protections.
None of those countries are communist. They have large social welfare states, and tax rates that might push 50%, but essentially rely on the free market for most economic decisionmaking.
In many ways China is closer to pure capitalism than most countries on the planet. The vestiges of "socialism" primarily live on in their authoritarian government, restrictive social policies, financial repression and massive state-owned-enterprises. China is slowly moving away from the latter two as their massive problems are uncovered.
Any economic system fails when practiced by corrupt or incompetent governments. There are many failed capitalist states, too.
Edit: if you want to talk about scaling, China and India are debatably doing well (or at least improving rapidly), and both countries have 1.3B people.
China had an interesting idea with special economic zones: let people opt out of socialism if they want to, but stay within the country and get basic protections.