"All power to the workers" is a communist principle, though. It's the main political slogan of the communist manifest by Marx and Engels.

Yeah, any economic system that concentrates power into one group is bad, whether it's corporate monopolies or a single government (which ends up kind of like the ultimate monopoly in a communist state). Communists IMHO have a fundamental misunderstanding of human nature and how incentives can be exploited for the benefit of everyone. We need a form of capitalism that promotes competition (because profit is possibly the most powerful motivator of innovation), but also keeps companies in check with strong regulations, strong workers unions, and profits taxed appropriately. It's also important to recognize that some basic needs should be met by the government like public education, public utilities, correctional systems, national defense, welfare, healthcare, etc. But even with public services, there should be room for private companies to innovate and provide premium alternatives to keep the government in check (with exceptions obviously, we don't want private military and private prisons for example).