Regardless of the art form, deeply studying previous works is the way to really understand how the artist created them. With drawing and painting it's learning

Regardless of the art form, deeply studying previous works is the way to really understand how the artist created them. With drawing and painting it's learning by literally copying them, and with jazz, it's learning by playing the same song and experiencing it for yourself. When you've internalized what the "masters" have done then you're in a better a position (certainly technically!) to create your own works. Of course Jazz greats such as Miles Davis etc would regularly play popular show tunes and use these as foundations for radical reinterpretation (eg. John Coltrane playing "My Favourite Things", Miles Davis playing "If I were a Bell"). If these guys had no qualms doing their own riff on something someone else wrote like "some day my prince will come" I dunno why anyone else should feel they're doing anything wrong doing the same.