I’m not sure spotifyd is just spotify (Edit: I checked, its some kind of spotify client meant to be run as a daemon? No idea what permissions that needs)

And the user that executes a service isn’t determined by who owns the service file, there is a user option in the service config

I don’t know much about systemd, but i assume the file should be owned by root? It looks like it isn’t, so try chown root:root spotifyd.service

Boot from a live disc/usb, check the kernel logs. That should at least tell you where the boot process got stuck, what to do about it depends on what exactly broke.