You' re gonna blame a coach because th WRs can't catch a football? Blame only the people who did the recruiting.
This is what I expect from position coaches on the team:
1. They must be good recruiters.
2. They must be good talent evaluators.
3. They must demand discipline and ensure that players to make continuous mistakes. In other words, they must have an immense knowledge of the position, and the ability to clearly communicate to the players.
4. If a player makes continuous mistakes, said player must be pulled from the game. Case in point is receivers who continue to show a complete lack of interest in blocking in the running game. This is a continuous issue. But as far as I know, no receiver has been benched, even for a couple plays, for this.
Of course a receivers coach is not responsible for players dropping the ball. But he is responsible for players running the wrong routes, failure to block, and unability to recognize coverages.