I use Phocid, maybe a bit too minimalistic regarding you used Musicolet. It is only available on F-Droid though.

• The metadata indexing (when the advanced metadata is activated) works wonders.
• UI is straight forward and simple and until now I did not encounter any bugs (LineageOS and e/OS).
• The folder structure is maintained and can be found under the “Folders” tab.
• Sound quality is good, way better than VLC (what I used before).
• Battery usage is, as far as I can tell, low