I am curious, why do you consider Glass a more innovative composer than, say, Reich? Reich's counterpoint and phase music seem to have pushed music forward more noticeably than Glass (outside of, perhaps, Einstein on the Beach).
Also you talk about counterpoint and incidentally early Glass sounds very contrapuntal (like early Reich) but I think a core message in Glass' body of works is that this entire bike shedding on harmony is so silly. There is so much to music beyond just pitch, and you can literally pick 4 chords and go crazy with it. He treats harmony as a solved problem. I think Reich would agree with this but I don't think his message is as profound. Think about Adams' "Harmonielehre" where he claims he wanted to combine minimalism and early 20th century harmony. The problem here I see here is that common practice harmony revolves around richness and variety. Fux himself says as much. It sounds gorgeous and new, but it doesn't go a long way to innovate anything. Although Glass' music sounds unserious, he actually tried to force himself to innovate. Which is what Schoenberg tried to do. Restrictions motivate artists to be creative.
Listen to Glass first string quartet, it was composed in 1966 before Reich's phase music.
[1] And of course his piano etudes but pianists insist they serve no pedagogical purpose, even though I still can't find someone who can actually play them well except Maki Namekawa. Roll eyes.