He doesn't always get singled out, Booker draws a LOT more heat here than TJ does. It's only been recently this year that his shortcomings have generated a lot of conversation. For me, I turned on him after about the 30th time I watched his body language go south. I think he does good things and when things are going well for him, he's very valuable.
But I just don't think you can win consistently depending on a player that is as weak willed as him. He stops competing occasionally and that shouldn't happen and that goes back to his rookie season. If he'd been un-drafted and giving us this kind of play, he'd be a good 2nd or 3rd man off the bench which IMO is where he belongs. I'd have him there because he can't consistently create his own shot against an aware defense, something I believe your 6th man really needs to be able to do.