I use Auxio from F-Droid. It's quite simple (which to me is a benefit) and my only real complaint is how similar shuffle on and off look on Android Auto. It handles non ASCII titles correctly where some others didn't (from what I remember due to weirdness with the Android media store) and it picks up new media/edited quickly and reliably which can be a sore spot with others. I don't know how Android's media store is apparently so incompetent that most music apps don't work correctly using it.