What is lacking, as far as I can see, is the kind of private and personal instruction and guidance that an individual receives in instrument study, in knowing how to really grasp musical(/theoretical) ideas in a personally meaningful and practical way (as in, not as a separate subject but one which directly applies to instrument/musical study).
Actually, it's not quite as huge as it seems - at least not any huger than any other musical subject.
Is it possible to play, compose, or improvise without theory?
Of course you can play, compose and improvise without knowing anything about theory. You don't have to be able to analyze what you're doing in order to do it.
We are missing each other. I had written:"Is it possible to play, compose, or improvise without theory? I'm talking about the real thing, not stuff featured in exams with the stuffing knocked out of it. "
I didn't miss it. I understood what you meant. But my answer is still yes, you can compose, improvise without theory. Granted, it's better if you understand how it works, but I know people who write music (not write down on paper, but "write" as in "compose") who don't even know what the letters names are or that they're using dominants and tonics, etc.
Since you mention letter names and such, I know that we are still missing each other. We may need a different word than "theory" for what I have in mind. Music has patterns, structures, "stuff".
When I teach my students, I don't really do "theory" separate. I want my students to experience music, play it, listen to it, create it, etc. In that process, they discover what works or doesn't.
I like that. This is what I'm understanding from different people is the best first thing - experiencing music in playing it, hearing it, creating it. Then if we do get at "theory" for some reason afterward - written, orally, whatever - it relates to something we have experienced. We don't get a picture of a mushroom and think that's all a tree can be.
What I think is missing from a lot of theory learning is understanding the "premise" behind any given subset of music theory.