Legally, you're still absolutely the owner of the device. You're perfectly allowed to smash your iPhone into tiny pieces and make an art piece out of them. You're also liable for damages caused by the iPhone.

It's just that the device is constructed such that your choices of use are restricted to "use exactly as permitted by Apple at any given moment" or "don't use it at all". This is enforced by technical means, by reliance on components you do not own (e.g. cloud services or the OS software) and by other laws (e.g. copyright). But it isn't enforced by ownership.