Let's imagine a situation.
The economy needs x amount of chairs made in a year to satisfy the demand for chairs. Capitalists don't know this in advance since they only have one signal to work with: price. Once the economy feels a scarcity of chairs, their price will go up and incentivize the manufacture of chairs.
While the economy is not feeling a scarcity of chairs and their price has not yet gone up, money is being put to more productive uses. When the economy inevitably realizes that it does, in fact, need chairs, it's already far too late because all of the money is tied up in more productive ventures. That's where the financial system comes in.
Banks, CEOs, CFOs channel money from less productive industries into the chairmaking industry. Chairs are made and everyone is happy. Or are they? While the money was being channeled through banks, paychecks were handed out to their employees and their bosses. That money could have gone to people who were actually manufacturing real goods or providing real services.
Here's the deal:
Capitalism is inefficient as fuck and it has a whole class of leeches (bankers) profiting off this inefficiency. If the economy was centrally planned, a well-educated person with a PhD would have used scientific methods to foresee the need for chairs and money would've been distributed to chairmakers in the first place instead of hoping that the market will regulate itself.
It's stupid to claim that capitalism is efficient when it needs leeches (bankers) to service it lest the entire system collapses. How many people's labor is wasted working in the financial industry creating nothing of value and how much money is wasted on paychecks for those people?
Let's put things in simpler terms:
Communism put a man in space.
Capitalism OBLITERATED the middle class to give the rich banker man a private yacht.