You don’t use a DJ feature(/any recommendation feature) to play specific songs, you use the search bar. Again, a recommendation system that gave you just exactly what you asked for wouldn’t be a recommendation system!

Re:”play related music”, yeah clearly Spotify isn’t built for classical music. Maybe it should be — I certainly would vote for it to be a priority for a state-operated alternative! But calling a specific feature lazy because of a high-level corporate priority concerning content isn’t valid, IMHO.