The problem with this theory is that conscription in the North didn't start until late summer of 1863, and was pretty much a failure. Only about 6% of the Union Army was made up of conscripts. By 1865, on the other hand, about a quarter of the confederate army were draftees.
I stand corrected. Draft did not start till 1863. Overall the Union leadership in the East was not stellar. It took 2 years to shake out ths system. The fighting from Gettysburg onward, many Union divisional, brigade, regimental commanders were promoted from the ranks up, veterans and proven men, versus the earlier selections tainted by politics or inherited deadwood. The South lost the war in the West and at sea. These battles helped the Union accomplish the Anaconda Strategy which ultimately cut up and strangled the South of resources and ability to replace material and manpower losses.