I think you are correct though that a defensive war would have been a preferred plan for the south, but Lee's reasons for going into northern territory were very valid, as well as a high risk.
As long as we are pondering what ifs: In the spring of '61 Jackson ran the North ragged in the Shenandoah Valley. With about 15 to 20,000 men he tied up well over 50,000, he beat them on a regular basis and more forces were being sent. Jackson's troops could not long keep up the pace demanded of them, and it did not last. However,had his strategy been taught to others and applied into the border states of Iowa, Pennsylvania, Ohio Illinois and others sentiment against the war in the North would have been strong.
The south was, of course, out manned and out gunned and any toe to toe strategy would eventually have favored the North. The north did not need brilliant men to fight the war, they needed men who were willing to do what was necessary to win and that was Grant.
Neither side during the war had “brilliant” men to fight the war. All of the general offices of both sides would order a brutal head long fontal assault if they thought that was the only option available. Lee did it, Grant did it, Sherman did it, Bragg did it. The War is a good demonstration of group think when it came to tactics.