I still think you are minimizing the tactical role of a manager; especially in the National League.
The range of tactical decisions that a manager has to make is so small that I just don't see it as all that important. Bunt for the pitcher? Play the infield in? Pitch out? Compare the range of these decisions with what, say, an NFL defensive coordinator has to deal with. I just don't see how any special expertise is required to handle most of the tactical decisions that a manager makes.
As an example, I think Bobby Cox is, if anything, probably a below-average on-the-field manager. But I regard him as a great manager anyway because he's the best at clubhouse management, which is the most important part of his job.
I am not discounting your opinion because it's your opinion and that's fine but did you ever play baseball?
Not past high school, and not very long then. By the time we figured out that I was having vision problems and it wasn't necessarily just that I couldn't hit a baseball anymore, it was too late to get going again.
So. What kind of insider baseball stuff that I missed out on makes it so complicated and difficult for a manager to decide whether to pinch-hit for his starter in the 6th inning? When to bring the infield in? When to pitch out? This is not rocket science stuff. A high school football coach has to deal with more complicated tactical decisions than a major-league baseball manager.