I’m very much a beginner in BJJ. I spend a fair bit of time thinking about it, though.
I’ve heard, and my experience corroborates it, that learning BJJ as it’s often taught, as a sequence of moves, is not the best. That sequence you learned and practiced against an in resisting opponent, will not translate into actual sparring. Basically never.
What actually happens, I think, at least for me, is that you learn to recognize particular goals to seek in a particular situation, and a variety of . . . shapes, let’s say, that can be helpful for accomplishing a given goal.
If I’m in closed guard, I want to get the guard open and pass the legs. That’s the goal. Not the only possible one, but still a fairly common one, worth pursuing. I know I can do that while kneeling by angling myself and pushing down and then sort of swimming forward. I can do it standing if while hand fighting I stand up with one leg forward and one back, and push down on the legs and then sort of dive toward the torso while trying to keep limbs from getting in my way.
I could also try to tire out the other person (or rest up myself) by cupping my hands against the inside of their elbows, pushing my head onto their chest, and driving forward. Different goal, different shape, but still a goal and a shape.
Obviously, those are not very technical explanations of what to do, but that’s the whole point. Certainly for myself, once I start rolling against a resisting opponent, that’s as much as I can remember from a technique, when I can remember anything. You learn pretty quickly that when you try to think of a technique as a sequence of steps while rolling (“and then I put my knee here, and then I post my hand here, and then I catch an underhook, and then I step around to the side, and then”) it doesn’t work out so well.
And to be charitable, I’m pretty sure the teachers know that the sequences they teach won’t be remembered and wouldn’t be very useful, and that (even if they wouldn’t put it in these words) what is taken away from the lesson is goals and shapes, and that that is the only useful thing that could be taken away. In this day and age, though, I wonder if those useful things, or at least many of them, could be as easily learned on YouTube for free and then brought to an open mat to practice.