Music isn't a single skill, it's a big collection of skills, many of which build on others. 10,000 hours may get you to a point where you can play the instrument you've been practising but you might still be a total beginner at music theory, composition, conducting, recording, etc.

When we describe someone as a master or a professional, it's assumed that they've mastered more than just the mechanics of playing an instrument, since all of the most well known names in music have multiple skills developed at a high level.