Welcome! I enjoyed reading this post also.
Some quick feedback:
First, the piece is very long. My attention was held because of the title and intro paragraph (it promises to get at “where’s today’s Beethoven”) but I am a very fast reader, and I kept asking myself “ok, I get this is going to be about musical improv so tell me where’s today’s Beethoven”. I checked the scroll position multiple times while reading it. Ultimately I did not feel the piece paid off in terms of answering the question (though I did learn interesting things while reading).
I don’t understand what “cocoons” has to do with either the topic, or the contents. It seems almost unrelated to the actual point you are trying to make. I think it is intended as an answer to “we need to build these things in order to reenable improv” but the piece weakens as soon as you introduce that concept. It is not well enough connected to the rest of the contents.
I liked that you went into detail about the reasons you think improvisation is exciting; and I liked that it was backed up by interesting quotes from sources I trust.
The beginning seems kind of crankish. I think probably because it is addressed to Holden, and talks at a meta level about your own beliefs, personal story, etc., before diving into the actual content. You can cut all that and just start with “Abridged Detailed Defense”. Similarly, the end becomes crankish again starting with “A cocoon is a physical space”.
This is some very good feedback. I deeply appreciate it.
The idea is that cocoons enable unfettered improvisation. So you are correct that “we need to build these things in order to reenable improv.” I need to do a better job connecting that idea to the rest of the contents.