Your argument is based on him making imaginary shots, and blaming Lance Stephenson for not gifting him an easy shot. Granger has never been a high efficiency shooter, even at his best. Regardless, it's about what skills he brings to the table, which right now isn't much.
It's not just that he's shooting poorly, Danny's entire game has taken a hit. He wasn't doing much else on the floor besides missing long range shots. He wasn't moving well without the ball, he wasn't getting to the line, he wasn't defending well on the perimeter, he wasn't running the floor, he wasn't crashing the glass or creating for teammates, and worst of all he wasn't playing with any energy. Only so much can be blamed on the injury.
You claim Turner is inefficient and that is true, but he's PRODUCTIVE, which is what always gets lost in the efficiency debate. Danny wasn't productive or efficient enough. We don't necessarily need efficiency, we need someone who can be productive, and Turner is much better in many areas than Danny ever has been. Danny has never been a good passer or ball handler, and that is what Turner is good at.
Being able to take the ball to the rim and finish is one of the hardest things to do in a high level basketball game. A lot of guys can shoot. Turner can do that, and whether or not he shoots a high percentage, that is valuable, and something Granger has never been really good at, even before the knee issue.