Thing is I actually think Walcott would have taken one of those chances against city had he been in the same position as Gerviniho
The thing is though most of the players you mentioned had proved themselves at a club in their respective positions, Walcott hasn't.
Most people are just not convinced about him, whether it be on the wing or up front. If he was that good he'd have taken his chances when he did feature up front and convinced everyone that's where he has to be played. He's clearly not done that.
Had no problem with RVC wanting to goal, after all like you say at 29 he'd want to win things, if the club is not matching his ambition then he has to leave.
However, he could have left like Nasri did, like Cesc did, etc and i think more fans would have supported him instead of the backlash he got.