10,000 hours will make you an advanced student in a very competitive field, if you are the kind of person who will put in long practice into that field. It might still be a question of musical talent; the students in question would certainly be the ones born with talent.
Further, it's dedicated practice, not noodling around and not performing.
Finally, 10,000 hours isn't any kind of magic number. It wasn't enough to make those students masters, and I would bet that you haven't put in anywhere near that many to achieve a level of skill that satisfies you.
About the only thing that comes out right is that to develop a skill, you need to practice. Which, to quote my own least favorite phrase, we already knew.