Well, there is a reason for the simplification. The brain does all that, sure. But the idea is in my opinion, that natural processes must be very, actually extremely, simple processes. Biology shows us how high complexity is generally achieved by starting off with simple building blocks. I suspect our neural evolution is similar in simplicity. If this is so, then all the rest in the list: “to integrate the observations of the past, and make sense of the present. And to make decisions. And to solve problems. And to come up with plans to change the future” is the complexity that comes from the simple task of prediction for the “next” state of input.