Immune system is way old. Why is it just the complex algorithms we don't quite understand, that we think evolve quickly in mammals, but not the obvious things like retinal pigments, number of eyes, number of limbs, etc? Why we 'evolve support for language' in the time during which we barely adapt our legs to walking on flat surface again?

The emotional responses and desires are, to some extent, evolved, but the complex mechanisms of calculation which objects to desire have to be created from scratch.

The brain does 100 steps per second, 8 640 000 steps per day, 3 153 600 000 steps per year. The evolution does 1 step per generation. There are very tight bounds on what functionality could evolve in a given timeframe. And there is a lot that can be generated in very short time by the brain.