I’ve had a quick look at the indexes created on the PC version of Engine Prime - I suspect this is where the problem is as there are some indexes, but they only reference 2 fields - track Id and another value (e.g I can see filename as one, path as another etc).
The thing is, for searching, it needs to search track name, album name, artist (and potentially other fields in future EP versions such as the promised search in comments feature).
The indexes mentioned above are not enough, so the code will not be able to use them so the execution plan would be much slower than if they created an index containing track Id, album name, artist name, filename, track name etc.
There are also no indexed views for tracks, whereas there are for crates, playlists etc, which is why loading a crate is relatively fast compared to searching. An improvement would be similar to the index mentioned above - create an indexed view with the track Id as the unique field, artist, album, filename, track name as other fields.
If anyone is curious, I obtained this information through Microsoft SSMS and the SQLite/SQL Compact Toolbox plugin.