Saphroneth
Banned
It won't end immediately, but it will produce a very important psychological and political blow to Confederate legitimacy - having lost their capital and having to more or less abandon their capital state, and with the only offensive into Union territory of the Civil War consisting of the Maryland Campaign (which looks pretty disastrous in light of the subsequent capture of Richmond TTL) the Confederacy looks much less like a winner than it did OTL. This is going to combine with the loss of Virginia as a recruitment centre, and the loss of the industry of Richmond and of southern Virginia, to result in a fatally weakened Confederacy - while it may not end the war inside six months or anything like that, it will mean the South is much less able to cause damage or meaningfully contest Union advances. It also loses an important administrative centre, and is certainly not better off than OTL (or indeed in as good a shape).In addition I am not saying that the Confederacy can win without Virginia so don't try and make it out like I'm saying that. But expecting the war to end in the Spring of 1863 in this scenario is far too optimistic. Also in regards to desertions: First the other Armies of the Confederacy, specifically the Army of Tennessee are probably fine. There were next to no Virginian regiments outside of Virginia and the Tennesseians in the AoT stuck by for years after the loss of their state before their numbers entered a terminal decline. So while the war probably has under eighteen months left in it the fighting will not end.
At the same time, it's no longer necessary to blockade Hampton Roads, and Washington functionally no longer needs defending - this frees up huge chunks of the Union army and navy, and indeed a lot of the heavy artillery from the Washington forts becomes available. This means that while Lee's army may be the same size as it was OTL in early 1863 or indeed larger (counting the troops withdrawn from Richmond), it'll have to deal with an enemy army which is itself larger.
OTL the Confederate army peaked in size in 1863; much of that recruitment won't take place TTL, and to achieve the same relative industrial productivity per military man it'll prove necessary to allocate much more manpower to production rather than to the armies. It simply won't be possible to generate the same volume of productivity.
If you measure in terms of iron produced in 1860 to get a proxy for heavy industry, Virginia (largely via Richmond and environs) is two thirds of the productivity of the CSA and Tennessee is two thirds of what's left.
Of course, if capturing Richmond wouldn't be a massive boon for the Union, it does raise the question as to why everyone tried to do or prevent it so much...
And yet still an issue. And a terrible result to have.
While true, it doesn't really have any direct bearing on whether capturing Richmond at that time would be a good thing, unless we want to excuse any mistakes made in the first half of the Civil War by claiming they brought Uncompensated Emancipation closer.
For what it's worth, McClellan's original plan for the war was essentially to bring it to a swift close by explicitly rejecting emancipation as irrelevant to the issue of the war, as this would indicate to the Confederates that their fears were unjustified; this of course from our modern view would raise questions, but it's worth asking oneself how many lives earlier emancipation is worth in the first place. If the Civil War had seen only 80,000 dead but Emancipation was delayed by a decade, that's a trade which is worth weighing rather than dismissing out of hand as one-sided.