Google Assistant commands are not very useful if it never plays your music. "Play <song> on spotify" never plays something from my library. This is also annoying when there are several recordings of the same piece by different performers.
To improve google assistant I recommend adding this command:
"Play <song> from my library" this will then search only your library/downloaded music and play the closest match.
"Play <song> preformed by <artist>" For example play "Sibelius's second symphony" preformed by "Berlin Phil" this can be implemented for general search, but could also be combined with my other suggestion.
Hey! Thanks for coming to the Spotify Idea Exchange. We've been keeping an eye on this submission for an extended period of time, and it doesn't seem this will reach the votes necessary to put it forward for prioritization. As such, we're marking this case as closed. This includes any similar suggestions that are received.
If we do have any new information to share, rest assured we'll check back in here with a new status.