So as you say learning doesn't stop at black belt and there are high level competitors who make all others look like beginners
The frustration of BJJ is deeper than that I think
For us non-professionals there are (or should be) times when you try new things out with lower belts, fail and get punished as a result
There are the folk that usually you tap who one day figure out how to pass your guard, surprise you with it and punish you as a result
There's the bigger or younger or more athletic lower belt who taps you regularly
There is the fact that all your training partners progress at a similar rate so you never feel like you're getting better
etc etc
My other style holds endurance as the most important characteristic and I think this applies to BJJ
The frustration of BJJ is deeper than that I think
For us non-professionals there are (or should be) times when you try new things out with lower belts, fail and get punished as a result
There are the folk that usually you tap who one day figure out how to pass your guard, surprise you with it and punish you as a result
There's the bigger or younger or more athletic lower belt who taps you regularly
There is the fact that all your training partners progress at a similar rate so you never feel like you're getting better
etc etc
My other style holds endurance as the most important characteristic and I think this applies to BJJ