Not everything is written in books or taught in classes, even the most accomplished genius is going to have gaps. Depending on the person and they're penchant for studying outside of the curriculum, those gaps could be relatively smaller between people, however it's not going to erase them. Someone who has already built a live system, potentially multiple times, is going to have experiences you cannot just intuitively reason through, you must live them. You don't need a majority of folks like this on the team but one or two could save you a lot of wasted time and effort.