In his book, Great at Work, author Morten Hansen begins with the production concept of doing less and obsessing more about you are doing. Highly productive people prioritize what they want to do and then really focus on doing those things really well.
Many people love doing a wide range of photography while others have specific subject matter for which they refine their techniques. People who turn pro often succeed when they specialize. They become best known for one type of photography. When we think back on the masters, who do we remember? We probably best remember those photographers who were known for what they photographed and how they did it.
They excelled at something specific because they prioritized it and obsessed over it.