You're right. So many people do not cultivate their utmost human potential because THAT would involve a LOT OF WORK and RESPONSIBILITY. As a result, many people are quite content with mediocrity until it is TOO LATE to change. Then, it's REGRETS.
I don't think humankind fears or avoids potential greatness. I think people aren't motivated enough to do anything to improve humanity, because the illusion of us being mere citizens, as opposed to powerful people, is much stronger than the desire to be great (which would require stepping outside of the comfort zone).