Every communist regime becomes authoritarian; none has proven otherwise. But we can see many examples of successful capitalist countries with democracy and freedom, even though they aren't perfect.
Capitalism may “work”, but it’s definitely not sustainable without checks and balances and limits on wealth accumulation and influence. Allowed to roam free, it’s disingenuous to say they “aren’t perfect”, they’re destroying the planet and its people.
Personally I’d be more in favor of socialism. Even that requires a lot of retooling, and most countries would have an easier time with more regulated capitalism backed by more socialist governments.
I don't see how this wouldn't apply to so called working communism, if there is any