at this point bitching about captcha is a slide . . .
there are more layers. People with burner phones are like those sniper guys lighting a cigarette: the enemy will see the burning ember and that's the end of cigarette smoking sniper . . .(it's from an old movie).
there are other layers of infrastructure.
the model of 'mac address' and 'ipv4' is an abstraction that is given to cell phone developers, the real infrastructure is deeper and far more complicated.