Managers are only as good as their players performances on the field.
He has 13 position players, he starts the best 9 most every game, it's up to the players to do their job in between the lines. They aren't.
When you have a team BA of .228, OBP of .309, and OPS of .677, Your best hitter (.266/.370/. 395/.765) is a 33 YO 4th OFer that had to play in Korea 2 seasons ago. There's not much a manager can do.