There are advantages and disadvantages with the prepopulated lists. You avoid user typos and misunderstandings, but as the lists are now, we are presented with a long list of slightly different versions of the the same song or a long list of artist that have performed that song. As the score that I have and the style that I download is not made specifically for one version, then what version or artist to pick? I try to pick the version that has the simplest song title, without "extended version", "live at", "remastered", "aqoustic version", "from...", "feat..." and so on. For the artist, I try to pick the most original artist or the most played cover artist. If someone else has already assigned an artist to a song, I stick to that, rather than connecting the song style with another equally possible artist.
But it is no doubt that when more people contribute, then more different artists and song names will be used. I am very happy to be able to find "every song and artist in the world", then I can suggest styles for local songs and artists (in my case Scandinavian), but I and this site may be don't need all the variants. It may be difficult to find a better database, I can see that.