For any beets users, I just released a plugin to apply MusicBrainz genres (and other configurable tags) to your library. It looks at both releases and their release groups, finds the most popular tags, then filters them based on vote count. If no genres are found at the release/release group level it can also fetch genres from the artist. If anyone gives it a try, let me know if you’re missing any configuration features or run into any problems.
Repository:
Documentation:
https://github.com/mistwyrm/BeetsPlugins/blob/main/README.md#musicbrainz-genres