This is a man who has been pushing the boundaries of realtime graphics since Wolfenstein3D. We owe him a lot, and I think he has earned the right to work on whatever project he damn well chooses. People seem to imagine all the amazing things he could have done with his time while glossing over the amazing things he has done right here, right now.
No, Rage is not the panacea of interactive entertainment. It is, however, a stunning showcase of some amazing new technologies in the form of a fairly conventional shooter. It is what it is, don't like it, don't buy it.
Nowdays, anytime an id game is mentioned you can't help but be overwhelmed by the "id games are teh suck!" noise. Fine. Don't buy them. But concocting some conspiracy about Carmack being held hostage by the artists or whatever is just nonsense.
He has a team of artists who help realise the (visual) potential of the awesome new tech he has developed. The gameplay itself comes second. Heresy, I know, but this has been the pattern for a number of releases and if the id team are happy with that then more power to them.
No gun to anyones head.