1. You're assuming all players accept guidance and direction from the team's coaching staff. This isn't true. It's not true in baseball or hockey from what I've read and heard. It's known that the Jays have flown in Vlad's team of relatives because he generally refuses to entertain suggestions from the Jays. To what level? I'm not 100% sure, but definitely mechanics related. I'm not entirely sure if this is still the case, or if Vlad has opened more recently. There are lots of professional athletes who only "trust" a select few (those who they've had success with in the past).
2. AA was on the Fan 590 a few months ago and when asked about their offensive woes, he said "if we knew what was wrong, we'd have fixed it already". I mean I guess you could conclude that AA and his coaching staff are all just "bad coaches" because they can't identify and/or fix the issue...but I somehow doubt that's true. To me, that was more clear evidence that A LOT of his is outside of the coaches control. The last time I raised this, I was told "it's just a SSS"....but the Braves offense has actually gotten worse and AA is now so desperate for a solution to their offensive struggles that he had to go trade for a 2nd fulltime DH in Soler.
I simply think the impact of hitting and pitching coaches (along with all their supplemental coaches) is a lot less than most fans believe. I also say this as someone who's EXTREMELY passionate about coaching.