While I strive to be a master of my craft, observing the world yields interesting insights. Many of the successful people I respect are not masters of their craft. The alternate path is to be in the top 25 % of multiple fields. One great example is Scott Adams of Dilbert fame. Scott failed his way to success by leveraging his corporate career, learning to program, getting an MBA, writing well, persuasion abilities, his above average sense of humor, public speaking skills and ordinary drawing abilities. Combining those skills makes Scott Adams unique. His heuristic is learning any new skills doubles your chance of success.
The other person I can think of is Patrick Mackenzie of Bingo Card Creator fame. Patrick or patio11 combined his programming abilities with marketing, A/B testing & writing to become an internet celebrity and a successful bootstrapped business owner.
My own inclination is to diversify skill sets with concentration towards one or two primary skills such as Programming or Design. Further augmenting it by getting good at a few other skills based on your interest. My path forward is to expand my knowledge of business , finance and machine learning. I would love to know the path you have taken.