We are no longer surprised by the importance of Genre. After researching this and getting a ton of feedback, we released that this is one of the most important user “owned” fields that exists, as most tools allow it to be edited. Your initial email to us is what triggered this investigation. This is also why we treat Genres very specially in our data model, and allow for you to turn on and off all Roon and all file tag Genres independently.
Your genres are not a hierarchy because your file tags have no standard way to convey hierarchy, so instead of making up a category for them, we chose to put them into Uncategorized and let you edit them into whatever hierarchy you want. Some users like the Roon genres because they come with an acceptable (to some) hierarchy and many come with descriptions, and just want their file genres to map directly on to Roon genres, usually due to spelling and punctuation.
The world of file tags is pretty diverse and despite many “standards”, it is not very standardized. We import some of the file tags that we recognize. The list was noted in the v1.1 release notes: Roon 1.1 Is Live!