I came across this via Y Combinator. I can only echo, pretty much word for word, Eduardo Garcia’s letter:
Please let me unlink my Facebook account
Last updated: October 14, 2018
It was 2014. I was young and reckless. When I saw the big blue button that read “Sign up with Facebook” I just couldn’t resist. Now, four years later, I want out.
In the light of the recent Facebook data breach I have decided I no longer want to use my Facebook identity to log in to your service. I am aware that the official recommendation is to cancel your current account, create a new one and manually move your playlists or contact support to do it for you, but I believe it would be better if you offered a straightforward way to do it.
As a quick search on your Community site reveals, I am far from the only person who would like to fix this. I can assure you all of us will be very grateful if this is implemented soon.
Sincerely, a Spotify user.