I also had a quest to build the ultimate music player. My motivation was that most music players got complicated to the point I was unable to use them.
My player is 200 lines of Python, utilizing MPD and Qt (for Docker icon), and has about 3 features. It plays all the mp3 in a directory (including subdirs) randomly, and you can "like" or "dislike" song, which modifies the probability of it being played (and these data are remembered in MPD database). Also has "pause" and "next song" buttons (from the tray menu) and that's it, literally.
To each his own, but that's my personal definition of "ultimate".
My player is 200 lines of Python, utilizing MPD and Qt (for Docker icon), and has about 3 features. It plays all the mp3 in a directory (including subdirs) randomly, and you can "like" or "dislike" song, which modifies the probability of it being played (and these data are remembered in MPD database). Also has "pause" and "next song" buttons (from the tray menu) and that's it, literally.
To each his own, but that's my personal definition of "ultimate".