Well first, it would be great if you could clarify what kind of mechanism you believe organisms could be using the drive their own evolution, but for the meantime I’d just like to address one of your “too complex for randomness” examples: insect pollination. I’d never be able to provide an example for every “too complex” system you can think of (as we could likely go on forever), but perhaps I can help you see how small random mutation can lead to very complex systems. A large portion of this response is copied from my answer to a post on /r/AskScience.

So you start off with a generic butterfly (really some ancestral insect species) and a generic flower (really some ancestral plant species). The relationship between our butterfly and flower likely started by chance. A flower had a mutation that made it produce a tiny bit of sugar. This is a seemingly bad mutation since the plant is wasting some of its energy stores. A butterfly notices this bit of sugar and eats it (completely self-interested). The butterfly happens to brush against the pollen producing structures of the flower and some sticks to its feet. This butterfly then visits other similar flowers in search of more sugar and inadvertently delivers some pollen from the first plant to a second.

This sugar leaking mutation has been of slight benefit to the flower (now its pollen is delivered slightly more efficiently than by wind). So sugar leaking flowers become more common in the population. Now the butterflies would benefit from recognizing the sugar producing plants and visiting those. One lucky butterfly happens to have a mutation that makes it attracted to red, the color shared by our sugar leaking flowers. This red attracted butterfly benefits from finding sugar leaking flowers more often and this mutation become more frequent in the butterfly population (mutations for attraction to green and black color were not so fortunate). The flower and butterfly populations will continue to have mutations (like all natural populations) and some of those will make them more successful at cooperating. The flower may begin to produce more sugar to ensure the attraction of a butterfly and the butterfly may develop finer and finer senses until it only visits one type of flower.

Hopefully from this you can see that even very complex systems can be broken down into tiny steps, which can be favored through natural selection. It is important to note that the steps that I have listed are not necessarily the ones taken by the first pollinators, but simple serve as an example of how such a relationship could come to be.

Keep in mind that for your proposed “self-driven evolution” to work it must have a stronger effect than that of selection on random mutations. So if the brain development of humans was driven by humans, it must be by some mechanism that would be stronger than the supposed selected against decrease in physical attributes. Or the brain development and decrease in muscle mass was advantageous and resulted in more successful offspring.