I suspect that, for a fair number, lack of enthusiasm for JT may have its origins in comparison with Anthony Randolph. He was, after all, the guy a lot of mocks had us taking, he made perfect sense for our roster, and I'm sure that I wasn't the only Kings fan who, on that draft night, was chanting his name while waiting for the pick. It didn't bother me too much that JT got picked instead, in most of the obvious ways they are very similar, and while I had doubts about his defense as compared to Randolph, I was willing to give Geoff a chance to show that he'd made the right choice.
So, we went through last year, and Nellie made sure that we wouldn't get too jealous -- as always, he left his rookie shorted on minutes (< 18 mpg). Randolph remained a semi-unknown quantity. And JT showed slow but steady progress through most of the season.
But then Summer League came along. Randolph looked like a HOFer, and JT looked like he absolutely did not give a damn. Sure, it's SL, and some bad players have looked great there. It proves nothing. And yet, I think that Randolph has now shown enough of his potential that he's established a presumption that Geoff goofed. Rather than just accept Geoff's judgment on the matter, I think more are now wanting JT to prove that he was the correct pick... if he can.
I'm thinking that's where some of the relative lack of enthusiasm for JT is coming from. It's partly him, but it's also the competition.