In the history of skills (guitar playing, mastery of swordplay, music composition, etc), it's not inconceivable that someone could go a long time and not happen to notice the same things that masters of the discipline have been taught. Most human endeavors and learning comes not by independent discovery of everything, but by building on what the people before us have learned. It's a rare genius who can skip that.

Swordmasters in the renaissance studied each others' books and teachings, much as physics students might study the publications of others in their discipline. The insights they each made might not have all been in technique itself, but sometimes in new ways of teaching it, or describing the nuances of what their masters ("no, do it THIS way ...") had told them in a different way which made it easier to teach.

For many physical endeavors, it seems like there are often a few Good ways to do something Right -- shoot a bow, hold a calligraphy pen, etc. You MIGHT stumble upon the best way to do it on your own, but it seems a little ridiculous to scoff that someone is "not creative enough" to figure out what nuance of technique they have been missing.