I'm far from a Lost Causer and I don't see how all that romanticization of Confederate generals is really connected to whether Gettysburg was actually a pivotal engagement and seen as pivotal at the time.
Those are good points but Vicksburg and the Western theater was smaller overall. The Confederate surrender at Vicksburg was slightly under 30,000 men with a few thousand more casualties, a little less than the total dead and wounded Confederates at Gettysburg. At Vicksburg it was most of the army, at Gettysburg it was only 1/3 of a much larger army. That's why I think it is valid to consider the Eastern Theater of operations more relevant and important for most of the war, as it seems it was seen by most people at the time. Not only was there a proportionally much larger population in the Eastern Theater and consequently much larger armies maneuvering in a smaller region but the US and CSA capitals were both right there as well. There is a reason
7/10 of the largest battles of the Civil War were in Virginia and Maryland. That's where the fighting was heavily concentrated because that's what the commanders and leaders thought was the most important and decisive in the short term. The Union capture of the Mississippi was decisive in the long run (like the capture of New Orleans in May 1862), but it's not like the Confederacy didn't get back on their feet and go on fighting for another almost two years in the Western Theater as well. Yes, Vicksburg ensured Union control of the Mississippi but it didn't end the war anytime soon. The Army of Tennessee defeated the Union two months later at Chickamauga and the Army of Mississippi was reformed in 1864. In fact it was Lee and Johnston who surrendered first in Virginia in April 1865 effectively bringing the war to and end, while most of the Trans-Mississippi took until May and even June to surrender.
If the ANV had won decisively at Gettysburg, I think that would have really tipped things in their favor more than any similarly sized victory anywhere in the West. Why? Because it was right there north of Washington. It would have been the ultimate blow to Northern moral which is exactly what the Confederacy most needed to win the war, either militarily or by preventing Lincoln's reelection in 1864. Instead the Confederacy was soundly defeated at Gettysburg, crippling their ability to launch further offensives against the North and consolidating Northern support for Lincoln as fighting a winnable war. To me that seems just as if not more important than Vicksburg and anything that went on way out in the boonies comparatively speaking.