Mitchell can (and does) blame the players all he wants, but his Raptors have become a purely reactive team because he coaches them that way.
I don't think I ever remember Sam taking a specific blame after a loss, but I've heard him many times placing the blame on the players (not naming anybody in particular). To me, that's a major sign of mental weakness and lack of confidence in one's ability. If you're good (and you know it), you will never be afraid to admit a mistake, because it's normal to make mistakes. I'm not sure if the players after a point start to lose confidence in their coach, but I would not blame them if they would.