Actually, MacArthur was vain and relatively unskilled. Except for deep political connections Roosevelt couldn’t afford to offend in WWII, he would have been fired early in the war. The existence of MacArthur probably prolonged the war in Pacific by at least 6 months and cost tens of thousands of lives.
The single honest success MacArthur had was dealing with post war Japan. That was his masterpiece and there he was the perfect man for that moment in history.
Inchon was a stroke of genius.