You are correct in that capitalism is a very simple system. It is based on the fact that all humans are self interested, and that they are allowed to pursue their self interests, which you are calling "greed". No one made capitalism up, it just happened because it goes right along with human nature. Nature isn't fair, and your animal analogy about a wild creature going to sleep without a care is a bunch of animal dung, and I think you know that. Some of my favorite animals eat other animals.
To change capitalism into another economic system requires coercion, because capitalism works, at least for most people in the USA. A planned economic system requires that everyone obey the plan even if it goes against their self interests, and that won't work here any better than in other country that has been tried, and it has been tried disastorously in many countries in the last 100 years or so. Or you could replace the self interested people with altruistic people, but there is no such thing as altruistic people. Even religious people help others out of the hope of heaven.
I try to do everything I do with passion, but I don't always get the opportunity to be spontaneous because the things I do involve other people, and they have to be considered. Planned economies have zero spontaneity to them, and you tend to spend a lot of time waiting in line with those other people. And what are you waiting for? Whatever piece of crap they have to give you is what. Since in a fair system everyone gets the same thing, there is no reason to make something of quality or that is superior since no one will profit from the extra work that went into it. Why even bother to make as many as were ordered if you recieve the same reward no matter what? So instead of waiting in line to get the latest Air Jordans, you wait in line to get an unfashionable pair of plastic shoes that don't fit.
Most people are not dreaming of making the world better by the way, they are just trying to make the part that they occupy better. Capitalism allows people who have wildly different desires and needs to fulfill at least some of them. The idea that everyone is somehow the same and wants or needs the same thing is a fallacy, and even worse is the idea that they can be forced to care about other people and work towards a common goal that doesn't do a fucking thing for them personally. The only way to do that is a police state. Capitalism doesn't care what we do, so it doesn't need to be constantly directing people to do this or that. Anyone who needs to be constantly directed as to what is right and what is wrong may find their perfect home in North Korea. They don't have capitalism there, and of course it is a horrible place to live.
