oh hey a post i can actually comment something useful on.
Fragile by Yes is an all time favorite for me, was my alarm clock for like all of elementary and middle school. Those songs seeped into my brain honestly, to this day when i witness great natural beauty i swear South Side of the Sky is just playing in my subconscious.
Gentle Giant and Gryphon have both been commented in this thread, my two favorite albums by them are The Power and The Glory (GG) and Red Queen to Gryphon Three (Gryphon)
Another artist i would highly reccomend is Van Der Graff generator, start with Godbluff and then move on to Pawn Hearts. Godbluff is really lyrically interesting and almost seems to focus on telling a story each song, whereas Pawn Hearts is introspection.mp4
Tarkus, an album my ELP, is in my opinion the greatest album ever created. I'm actually strongly considering getting a tattoo inspired by some of the art made for that album. The 6th part of the first song, "Battlefield", is literally how I became super anti-war as a kid which was sort of a pipeline to leftism for me.
Then there's King Crimson, and honestly you can take any album from before Beat and you will probably enjoy it (not dissing Beat or anything after it, ive just never listened to those albums so I am not sure if they are good yet).
This is dope, thanks for sharing.