In most martial arts, the black belt is awarded based on time, attendance, and the ability to perform forms or sequences. In BJJ, the black belt is awarded based on the ability to apply technique against fully resisting opponents — week after week, year after year.
There are no katas in BJJ. There is no shortcut. The only way to a black belt is to roll, get tapped, learn, and come back the next day for a decade.
Less than 1% of people who start BJJ ever reach black belt. Most quit at blue belt. The few who make it through the entire journey share one trait: they didn't stop showing up.