Genuine question: if your Apple account is locked, and you're unable to create a new one, is your iPhone still usable?
So you could use your existing apps but not download new ones from the App Store.
You could use iMessage with some restrictions. You could use Apple Music but only the free radios. You could use Apple’s photos but would lose sync.
Usability depends on how much you rely on those services, but the device itself is still useable for other things.
It's against apple's ToS to avoid bans as such.
That said, I choose to use it this way and it does everything I need it to.