Sure, without autotune some people might not have had hits but the same goes for many acts in the past. To my mind, autotune does what double tracking and comping used to do but quicker, which saves on studio time. Your voice doesn't sound like that! It just irks me that there's a lot of people who'll complain about one aspect designed to make recordings sound better, while ignoring that massive rack of expensive equipment designed to make it all sound better. And if you think about it, even reverb is cheating.
So I think you're drawing a subtle distinction, not a big one. Why does it need depth added? It's still strictly cheating. It puts vocals more in tune as well as thickening, or depth as you put it. Modern day double tracking as generated by some autotune/harmony engines are very different. There’s a big difference between genuine double tracking, which is about added depth to a voice with no autotune etc… just a simple second take where you tried to match your timing.
