He hasn't had the time yet. There is no good pitching out there. I think he released those guys to do the opposite of what you say: to show the team he cares about improving the pitching and that they aren't going to accept poor pitching under his watch for long. I'm not upset about any of them being released.
If Perez and McCracken or even on the team at all, I'll be surprised. They were just here to add depth in case of a possible trade and to add competition during ST.
He hasn't had the time to show he's good or bad, but I like what I've heard him say. Let's give him time before we think he's an idiot. I personally think he knows what he's doing.