Practitioners and coaches have shared a great deal on reddit and various other social media and content sites about what the various jiu jitsu belt levels "mean" or what it takes to achieve them.
The least popular opinion is that, at least at the early levels, you should have a certain number of escapes, passes, and submissions available to you from core positions.
A more common opinion is that you should be able to perform respectably against a group of opponents of a similar rank.
Last night I was thinking through what separates me from the brown belts I know, and here is a mental model I thought held up to my half-asleep scrutiny.
Blue belts: should have familiarity with the basic positions of the sport and enough knowledge of the most common submissions that they can hit these reliably on white belts.
Purple belts: should be able to quickly and intuitively identify errors in an opponents decision making and exploit them without necessarily having drilled the position before.
Brown belts: should stop making unforced errors like rolling for a berimbolo on the wrong side or attempting a knee-cut without an upper body control
Black belts: should be able to force errors reliably by constraining their opponents available options to a small set with ready responses.
Over the past year I've been focusing hard on recognizing when I have only bad options available to me and proactively bailing on the situation in an attempt to reset. This has generally resulted in a small improvement in my guard retention and wrestling. I've been complimented a few times on my "judo" skills, and I think in large part its because I'm getting more standup experience because I don't concede takedowns and take a familiar feeling guard (giving up two points). I've also been trying to break myself of a habit of accepting bottom side control. For a few years I've developed a comfort in bottom side-control, where I rely heavily on americanas, triangles, buggy chokes, and waiter sweep counter attacks. This has been to my significant detriment in competition, because if I am in that position I am almost certainly down on points and my opponent does not need to risk exposing themselves to my counterattacks. My main goal right now is to stop letting my comfort in bottom side control allow me to concede the position in the first place. I've put in a lot of work to improve my ability to escape the position, but I need to not make errors which put me there in the first place now.