So, if he can breathe on his own, and swallow, take the guy home and care for him, what do you need doctors for?
But if he can't swallow, and if fed through a tube... now you're in a different territory. But "quality of life" is not usually the determiner, but "possibility to improve."
The guy could have lost all his cerebrum, but still have his brain stem and cerebellum. In which case he's at the point of a vegetable... but if his eyes track, then that is not the case. he still has his visual cortex.
The family should get another doctor.