If I was to review my career (which is by no means exceptional, but still), the times I've taken giant steps it has been either because of luck (I joined a company at a good growing point) or a mix of skill, luck and a network of people that help put me in opportunities to be exceptional. I have the skills to be great, but I need the opportunities to be great as well, and opportunities are not necessarily only created by skill.
Skill is a necessary component, but it is not the only component. There are a lot of things a lot of people can do, and the determining factor in who ends of doing them is usually not skill. There is such a thing as skilled enough, which is hard to get to, but if you're opting between getting 1% better at something and getting 20% better at something else, often taking the 20% thing will pay off more, whether that be in networking, finding more opportunities, or whatever.