I am lucky to have many talented musician friends, world-class performers at the peak of their game who can perform music at the highest level. Sometimes I’ll ask them what they’re working on. The answer I get is frequently the same: fundamentals— getting a good tone, playing with good rhythmic time, you know, the basics.
So why would high-caliber professional musicians need to work on the basics? I mean, don’t they already have the basics mastered? Don’t they teach you this stuff in fifth grade, how to produce a good tone and play rhythms correctly?
To answer in reverse order:
Yes, they do teach you this stuff in fifth grade.
Yes, professional musicians should have the basics mastered.
Because if high-caliber professional musicians don’t work on the basics, they will eventually lose their grasp on them and be unable to perform the more complex literature.