No doubt that calling a game has a huge impact, but if a catcher isn't good at it, those things can be signed in from he bench. It happens a lot. I agree that I'd rather have a good catcher who can do that, but a team can get by at the position by giving him lots of help from the staff. I agree that those calls probably have a bigger impact, but it can still be done even if the catcher can't do it very well himself. The pitcher himself actually makes the final decision.
The catcher is the only one who can catch the ball and if he can't do that, there really isn't a way to help him. It isn't so much about stealing strikes as it is not giving them away. Guys like Larue and Ross who aren't real smooth back there who swat at the ball to knock it down because they don't catch it well, cause a lot of close pitches to get called balls IMO.
I agree with you about calling a game having a huge impact, but for a position called "Catcher" seems to me that catching the ball is job 1. I might giive you the nod on the other stuff. A catcher needs to know the situation and the status of his pitcher.