I don’t use Musescore (although I do use Lilypond when creating scores), but I believe its playback relies on software instruments via MIDI, so the quality of the playback will depend on the quality of the software instrument. If you have high quality multisampled instruments it can sound quite good, but if you’re using built in synthesized stuff it can be pretty poor. It just depends.
(FWIW, you can hear some higher quality software instruments in a recent recording I made. Sorry, no recorder in this one, but the drums and bass are both multisampled software instruments played on a MIDI keyboard. Harmonica and guitar are real instruments. St. James Infirmary Blues)