I love Sufjan Stevens, but I don't see the comparison. While I really love his lyrics (one of the few I actually like them, I usually find most artist lyrics to be plain and way too cheesy), his music is very simple compared to a behemoth like Mozart.
Mozart was able to write highly complex music very fast, that went from deep themes to silly ones, and enjoyed popularity from both critics and public, which is something quite rare.
I don't which one would be the closest today. Maybe something like Williams or Ennio Morricone.
At this point I wonder if there are some internal politics that want this project to fail and be over. 70 price tag, live service but only on ubisoft platform, ignoring the most demanded features, etc.
It's like they are tired of a project that was a money black hole for years and they just want to pull the plug.