Why can't liberals figure this out for themselves?

As usual, you present a problem without a solution. While your point is well-taken, the fact is that if you got rid of the federal reserve, deficit spending, and so on, we would have an economic crisis of untold proportion. Marx's critique of capitalism is still correct. Capitalism needs ever expanding markets in order to support the ever expanding needs of a growing population. When markets contract, capitalism has no good answer except to artificially expand those markets with deficit spending. The fact that capitalism works better than communism does not mean that capitalism works perfectly. If the choice is feudalism, Communism, western socialism, and capitalism, if you look around the world, it's pretty obvious that western socialism (a capitalist/socialist hybrid) works best, but by no means perfectly. Even when our economy is at its most robust, approximately 1 in 10 people are living in dire straits.