The first person using Apple Music to join a league becomes the Apple Music rep for that league, which means we'll use their Apple Music account to create the Apple versions of both the aggregate and weekly playlists.
Links to Apple Music playlists can only be manually created in their UI, and we are also unable to add them to your library automatically. Therefore, the league's rep must manually share the playlists with any other Apple Music users in the league.
You can still open songs in Apple Music by clicking them individually, but this playlist situation is unavoidable due to Apple Music's API design.