It's perhaps rather ironic that people are moving away from music players that store offline music just as storage has become so cheap and plentiful that you could cheaply store, and backup, even upload to the cloud, loads of music that you own yourself and can move from device to device.
More and more people, myself included, stopped buying music years ago and signed up to a service like Spotify. Sure, I can download music for offline playing (and do so, with 50-60GB of music on my phone and on various other devices) but I don't own any of it, and must pay £10 a month until the end of time, or when Spotify goes out of business, or ups the cost or whatever.
Artists can remove their music too.
Generally speaking, however, I love Spotify but in 10-20 years if I ever decide to stop subscribing as I'm sure I will when I get old, then it's all gone. Nothing to sell, nothing to hand down to my son, nothing to take to auction.
Of course MP3s are much the same, but you do - in theory - still own the music and we might one day sort out the legality of passing on your digital purchases to a next of kin.
I say that without knowing if that's a thing being discussed anywhere, as I would hope it would be.