Can't say I'm surprised. He didn't want to fit in on an OKC team where he wasn't the guy. Passive-aggressively refused to shoot the basketball. Kinda wonder if his retirement announcement is a show of leaving on his own terms when the truth might just be that nobody wants him anymore. Ring-chasers need to fit in and help out where they can. He demonstrated that he would not.
I don't have strong feelings about him despite the fact that he is a former Celtic. So, uh... bye, I guess.
I have a feeling some of this is true. I can think of a bunch of teams where he can play a solid role, but he'd have to take a massive pay cut. Lakers, Sixers, Bucks, Warriors, Miami, Denver. I'd be surprised if none of those teams at least kicked the tires on adding him. He never became the guy he was projected to be before the injury, but he's still got good ball left in the tank imo.
But when he left Boston for Charlotte, it was clear winning wasn't his primary basketball objective - which I'm not hating on at all. That's his prerogative. It makes sense that once the large contracts weren't being offered anymore, he'd move on.