I think the nuance kind of plays out like this:
- hitting coaches probably have minimal impact to no impact on the majority of players
- therefore, from an outside perspective it makes the most sense to assume that the hitting coach is NOT the cause or reason for a certain player being bad or good
- however, there is a tiny chance that a hitting coach could have a significant impact (or, that a bad hitting coach could f*** up a player)
- therefore, it makes sense to employ good ones. The cost vs. benefit is simply there. How much does a good hitting coach make, low six figures? If you can get 5% more out of one $10M player, the coach is worth it. Not to mention all of the routine stuff they do (the 9-5 work).
So... they could be at fault but they probably never are.