We've already designed, or grown might be a more accurate description, working (most of the time) systems which defy understanding [in full] by the most gifted

We've already designed, or grown might be a more accurate description, working (most of the time) systems which defy understanding [in full] by the most gifted humans. See the world financial system, our national electricity grid, Windows, Wikipedia, etc. etc. We may not be able to design AI, but we are going to develop it.