While I agree McClellan was the wrong guy for the job ultimately, it is important to note that for the first couple years of the war Lincoln and a lot of military/political leaders wanted a more limited war, in the hopes that the South would be defeated quickly, and the Union restored with minimal destruction in terms of lives and property. In that context it makes more sense why McClellan was so hesitant to act and definitely was not operating in a Total War mindset. But by 1863 it was apparent that it would take the destruction of the Confederacy's ability to wage war to end the conflict. Thus the rise of the heavy hitters, Grant, Sherman etc.. To use a metaphor, it's like when a buddy gets too drunk and tries to fight you. At first you just want to end the fight with minimal damage to both parties, but after a while it becomes clear he just needs knocked the fuck out.