Not only can you not disconnect it, but it’s the only way it can work now. I had a problem with my Spotify account, and the first thing the support rep did was make me connect it to Facebook because he said he couldn’t fix it until it was connected.
So my many years old account just got forced to be connected to Facebook last month.
What if you don't have a facebook account at all?
I dunno maybe you have to sign up? I’m sure they have a way to not connect if you really push them on it, but I just didn’t have the energy to fight it.
I don't have Facebook and have Spotify... No problems
Spotify used to require a FB account when signing up a few years ago, but then apparently stopped. (Once I saw it was required I declined to sign up and have never been back, but that's what I heard.) Is it back to being required on signup now too?