And how about a slot for the prog-like bands: Yes, ELP, Gentle Giant, Caravan, Soft Machine, Robert Wyatt, Henry Cow, Happy the Man, Fred Frith, Pink Floyd, Art Bears, Crimson/Fripp/Belew, Jethro Tull, Art Zoyd, Present, Univers Zero, Mahavishnu Orchestra ..sorry, I got carried away. There's just so much music!
Finally!
A list I can relate to!
Without sounding too insulting, so many lists are just so predictable.
Back in the late 70's and early 80's, I used to work at a high end store here in Los Angeles*. And while I admit my memories may be biased, I certainly remember a fairly large number of people coming in to audition gear with some pretty challenging music, and pretty far from mainstream.
Bands, musicians, and composers similar to those on your list above, and my list previously posted, were not at all unusual.
Maybe because our store was very close to a record store that specialized in prog from all over the world? Hell, even Sherman Hemsley (George Jefferson) was a customer of the record store and the high end store.
And yes, there is so much great music similar to your list. And that includes contemporary bands in the same vein as the ones you listed.
*Audio Research, Magneplanar Timpani, Sumo, SOTA, Eagle. etc.