[johnny99]

Lincoln did criticize his generals, eventually removing McClellan from command for timidity. He was careful about how he did that though, and how he interacted with the rest of the general staff. But he proved to have a better grasp of strategy than most of them, which he was able to implement once he found Grant.

You're correct he was reluctant to overtly criticize, but the lesson to take away isn't to just not criticize. It's to be diplomatic and patient when trying to effect change. Being a natural leader, brilliant, and with great strategic intuition also helps :-)