This is for the common gym (and follows what was developed as class structure in the early days in Brazil), not for the more enlightened gyms that exist but they are not (or not likely) for the common person. Say, for 100 gym, 90 are set up the way I describe above.

The technique section is like going to a seminar whose topic you didn't choose and whose content you won't likely see again for a few months or years. Like, today we do partial differential equation, and we will do them again in 6 months from now (apart from some of you who like them and decide to practice with no support).

There is very little effort to present the common processes that make a technique work or not. For example, in ML you have broad categorization of approaches, such as supervised/unsupervised/reinforcement learning. Within supervised learning, you then have classification/regression. Then within those buckets, you have linear, non-linear. Within non-linear, you have bagged or boosted or neither. They share commonalities at different levels and they help the practitioner learn the techniques much faster and then apply those technique in a creative way.

Likewise, in mount and side control you have similar need for hip control, shoulders on the mat, diaphragm under pressure for the more pressure-oriented jiu-jitseiro. But more often than not, the side control technique of the day is presented as just the technique of the day with very little connection to other techniques or common processes that make the technique work. A waste of potential deeper learning.

More often than not, the instructors/coaches/professor love their voices and presentations way too much -- 5 minutes of explanation regarding some details of little relevance while students are getting cold and unfocused, then 5 minutes of drills that take 3 minutes to start because students have forgotten what the coach has shown (and you can imagine how long it will remain in the mind of the average practitioner after the class is over).

Then, we have sparring, which in JJ is for some reason way too high stakes. In judo, you see top people getting thrown or give points all the time in randori/sparring with no ego bruised (well, more in judo than US wrestling, while in Russia for example you see more learning-oriented sparring, in the US it is grind, grind, grind), but in JJ, especially after people get their blue belt, they absolutely do not want to get chocked, arm-barred or swept by equal or lower belts. This creates defensive games that make thee knuckles white, but give little back in terms of improving the game of the practitioner.

Positional sparring is pedagogically much better than free-sparring, since the same position or situation is presented or needs to be faced multiple times and that creates lower stakes, less defensive sparring and more "learning". That's the drilling that matters (and see Dave Alred's repair sessions https://leadersinsport.com/performance/dave-alred/) and what for example Roger Gracie, the best JJ sport practitioner of all time) does.

Many other points to discuss, but the main point is that coaches are not trained in coaching, they have no idea how to present ideas or concepts (clearly, there are exceptions and they are very often the most successful gyms, although there is selection bias at work), they are "just" good at JJ and they went into coaching.

Some might say: but some people are getting very good at JJ. I agree, but "sink or swim" is a selection approach, not a teaching one.