As you say, the key to skill improvement is playing deliberately and getting meaningful feedback in a tight loop, ideally at the edge of your abilities.

But there are many aspects to any complicated skill, including tiny subskills, combination of various subskills, and at a higher-level meta skills like knowing when to change strategies, etc.

The problem with only sport games as a mechanism for feedback is that (a) there’s not necessarily a good way to correct and try again right away if you want to practice one particular thing, (b) situations that arise are not homogeneous enough to compare feedback across trials, (c) there are periods of waiting in between direct practice, (etc.?).

As a result, people who are training to be basketball players spend only like half their time playing realistic games, and the rest of their time on a variety of drills and workouts including general aerobic and strength training, practice running sideways and jumping, shooting / passing / dribbling drills, practice setting screens / rebounding / driving / inbounding the ball, larger-scale coordination drills, and so on. These let the players focus their conscious attention at one level at a time, and repeat a situation with analytical feedback in between.

But those who improve fastest are the ones who figure out what they need to work on (or have a mentor/coach to figure out what they need to work on) and then get lots of feedback about that particular area, in an intentional way. This can even be done within the context of a realistic full game by choosing what to direct attention/focus to.

But you’re missing my basic point, which is that all the skills in basketball are situated within a context. It’s obvious how they fit into playing a game. Students start with the high-level context (by watching / playing full games), and then break it down into small pieces they can work on separately or jointly, and then frequently practice putting those pieces fully back together in the context of the game. I doubt you’ll find anyone seriously training to play basketball who doesn’t play in a semi-realistic game-like situation at least once per week.

In classroom education, often the high-level context is completely missing, and students end up memorizing / drilling on a pile of atomized facts and trivial very low level skills without ever practicing combining those in larger settings, without ever getting a very fast or effective feedback loop going, and without ever having any motivation for going through the practice.

In the case of mathematics education, someone being taught 1-on-1 by a skilled tutor can move I’d say about 4–10 times faster than a student only watching lectures, doing completely independent book reading / trivial homework exercises / quizzes, and then getting back graded homework/quizzes a week afterward. That student can be assigned dramatically harder problems, can be helped along by limited (but well placed) hints, and can be given direct feedback/corrections at every level (from basic arithmetic computations through higher-level strategy to meta skills like strategy selection/evaluation). This is something that can’t be done in basketball because basketball is a group activity; you can’t watch a single player go through the game, and pause/backtrack everyone to the beginning of a situation whenever that player makes a mistake or suboptimal play.