Supply lines stretched too thin and insufficient troop numbers. Like I said, the jury is still out.
After Gettysburg, the Richmond newspapers were full of criticisms and advice...
Lee wrote to Davis... (paraphasing) Obviously the wrong people are in charge of the Army. Why is it that those who know best sit at home and write editorials instead of going to war. The Confederacy would be better served if the editors and the generals changed positions. Then the editors could lead the war effort, and the generals could critique their effort.
I have little to no respect for after the fact critiquing. The friction of war and fog of war changes strategy from the moment the first boot hits the ground.