1. People think they already have the fundamentals 'down'
2. Actually mastering the fundamentals can be boring and make a game feel like work (which, if you don't truly enjoy pushing the limits in a game, it is.)
A totally random example from League of Legends. 99% of players go into game after game and literally never review their previous games. They will spam games but literally never go into a custom game to practice last hitting. Or, they'll play a different champion every game, instead of putting in the repetition required to fully comprehend all the matchups they will find themselves in.
In short, very few players think of their most time spent practicing fundamentals as a valuable investment. Related, most players never even learn what the fundamentals are because revealing them takes a lot of effort.
For example, Starcraft is a game largely driven by economy or 'macro' rather than ultra-fast reflexes. However, the importance of macro is basically hidden from novice players. Their in-game experience is 'the other player always has more stuff than I do!' which they often attribute to build-order or other game decisions. It actually takes a while before a player really gets in tune with the idea that they need to be deploying resources ASAP and balancing the resources they acquire with the unit composition they are going to have in the next [insert window of time].
3. Mastering the fundamentals can just be hard. E.g. movement and aim in most first-person shooters. Mastering these fundamentals can be hard to the point of even professional players having significant gaps, e.g. players that are known to have excellent movement but lackluster aim, or vice versa.
Raw aim = mechanics.
Crosshair placement = fundamentals.
Basic Movement = mechanics.
Pathing = fundamentals.
You're absolutely right about things just being hard though. The gaps between even professional players can be huge in one area and nonexistent in another. Once you take that and apply it at the team level, it's easy to understand why a player could shine among a certain group, and do terribly with another, even if both groups were of very similar 'skill.'
However, the key isn't necessarily video recordings. It's deliberately practicing individual things you are bad at in isolation until you are good at them.
We need to record LoL and StarCraft games because it's tough to pause and redo something in the middle of a match. Similarly recording baseball swings or people dancing or swimming is useful for reviewing the complete action.
But when you practice piano, you can pause and redo a measure or line until you get it right, then slowly reincorporate it as part of the whole piece.
The WORST thing you can do is keep playing and think "I'll fix that later." Because inevitably you'll play a piece again, probably do the same mistake, and now you're actually practicing the mistake and ingraining it into your memory.
A video recording and reviewing it of a whole piece can help you go back and isolate your mistakes though. But it's just a tool for the goal of identifying and fixing mistakes.
We used an iPad to record swings of our little leaguers and it made a huge difference for them.
It helps because it’s easier to see what is happening vs hearing it. One example that we would see is kids dropping the back shoulder when they swing. Once they see it, they correct.
My wife had trouble with a certain move in dog agility until she saw herself do it on video and it was clear what was wrong.
I only box casually for fitness but I like that the teacher tries to teach good habits.
It's pretty hard to go straight from DATA -> ACTIONABLE COACHING DECISIONS
It's much easier to go from COACHES INTUITION + SUPPORTING DATA -> COACHING DECISION
I'm not aware of any other coach (but there probably is some) that has the technical skills to build the kind of tools that would be required. Bear in mind, most games don't actually give you all the data you'd want to look at. That said, there were a few folks who made a killing in esports betting for a while.
A direct experience report on the same topic from a particular game.
Can you clarify this? Is this because most people don't care about mastering the fundamentals in the first place? I can't tell whether I'm missing something and the idea is more complex, or that's what you're saying.