Doing that I can see the loading bar for half a second when reopening the app. As stated on the app webpage this is certainly to update the database with any new images but it doesn’t rebuild the entire database from scratch.
Maybe your cache gets deleted automatically when you close the app on your device. Make sure you have no other app that may do so.
Looking for something else I ended up on MusicPlayerPlus which may check lots of the boxes, especially those not covered by ncmpcpp which is my favorite mpd frontend.
https://rybczak.net/ncmpcpp/ https://github.com/doctorfree/MusicPlayerPlus