The Confederates did not have the freedom of Russia or, perhaps more closer to home, the Colonists in the Revolutionary War. They didn't have a vast continent to fall back into and draw their enemy further and further into hostile territory and away from their supply base. The Confederacy was bordered by the Atlantic to the East, the Gulf of Mexico to the South and their enemy to the North and West - to a lesser extent - no matter how far the Confederates withdrew they could not stretch the Federals logistics far enough for it to impede them.
This being the case they were never going to win the war with, what people term as, a Fabian strategy. The more passive cautious kind of warfare favoured by Joe Johnston would have preserved lives and kept armies in the field but that field would have diminished considerably with every bit of territory relinquished and with it the means of supplying those armies as well as the very purpose for fighting.
It would only be a matter of time before the predominance of manpower and material at the Federals disposal would come to bear and crush the Confederacy under it's sheer weight. To achieve their aim of secession becoming perminant the Confederacy had to be agressive, it had to be reckless, it had to take risks. In this Lee was the ideal commander because he was a risk taker and he was agressive and he was, at time, reckless.
He gambled big in the hopes of winning big, and that was, really, the only chance the Confederacy had.
I maintain that, if Lee's gambles had paid off, simply holding the Federals at bay in the West would have been enough for the Confederates to succeed but they failed to do even that, so it's kind of a moot point.