Lee discourse in general falls victim to the issue that the modern values system correlates competency with morality. Lee is a horrifically brutal slave owning traitor who should have been hung along with much of the ANV's leadership. He was also one of the finest commanders the US has produced.
Eh, the other half of the "Lee was overrated" discourse was countering this kind of Lost Causer discourse: "Bobby Lee and Stonewall would have ended the war in six months if they had the North's resources! Your boys Grant and Sherman were fighting the war on Easy Mode and they still nearly choked!"