We are forgetting that Managers no longer have the sort of control over day to day decisions that they once had. The Spread Sheet boys have much to say about it now.
That said, from what I can see, I really don't have an issue with Cora. I would be willing to bet some of the in game decisions are coming right off some computer geek's data and forced on the Manager.
As for the pure rest days (not driven by a game matchup), that IS likely Cora and as much as they might frustrate us, how many key injuries to everyday players have we had in the last two years? Pearce, Moreland, Pedey, Holt this year....Pedey, Holt last year???? How important are any of those players? JD is about the only guy I can think of that is important to this team's efforts that has had some injury issues this year. I would hope Cora has learned his lesson about JD in any OF position that is a challenge, like ANY Fenway Park OF position for example.