To an extent I agree with you, but not entirely.
Yes there's an onus on the players to go out there and play to a plan as the coach has instructed them to, but there is also an onus (in the end, this IS the job) on the coach to be able to get that response from the players on the field, based on the training, preparation, planning, and group and individual discussions before a game.
If Wayne Bennett sides consistently turn up ready to play, get the basics right, and have an intense attention to detail for 80 minutes then is it not fair to say that his coaching is capable of achieving that? Is it not therefore fair to say that if a coach (such as Stone) is repeatedly unable to make this happen that it's an area he is lacking in?
I'm not suggesting that a coach can catch the passes and make the kicks for his players, but when the 80 minutes is full of a variety of mental lapses such as forward passes getting out off our own goal line, penalties in the ruck right at the start of a match, silly penalties in general, hospital passes in slippery conditions that don't need to be thrown, failure to kick long and chase hard, failure to use the grubber in an attempt to force repeat sets (especially in the wet!) etc etc then yes, I do apportion blame to the coach for this.
If he can't stress how important a solid game plan is to his players then he is only doing half the job of a coach. I'm sure he's not teaching them passing and kicking techniques, so the area he is mostly going to be judged on is on-field structure, discipline, and game plan.
Another thing that bothers me a lot is that the small period in the second half against Dragons where we fired up and brought serious intensity to try and get back in the game is not something we ever manage to do against lesser sides when that sort of attitude would get us the 2 points.