The stereotype of Napoleonic Warfare and indeed any gunpowder war before the World War 1 is that soldiers just line up and shoot without regard to marksmanship because they assume that an enemy will get hit in the mass fire of volley. So much that I seen comments about how you don't even have to hold your rifle properly and you just shoot it in the American Civil War and earlier because you are guaranteed to hit an enemy in the mass rigid square blocks they are stuck in.
However this thread on suppressive fire in modern warfare made me curious.
https://www.reddit.com/r/WarCollege/comments/7vkubw/how_important_is_individual_marksmanship_is_in/
The OP states despite the cliche that hundreds of bullets are spent to kill a single enemy and most tactics in modern war involves spraying at an enemy to get him to become too scared to shoot back and hide while you have one person sneak up behind the now cowering enemy and kill him, plenty of marksmanship training is still done in modern warfare.
So I have to ask if marksmanship was important even in volley fire seen before WW1 in the American Civil War and other earlier time periods in particular Napoleonic? Is it misunderstood much like modern suppression tactics is by people where they get the wrong impression that you just spray bullets on an enemy and marksmanship doesn't matter because your buddies will sneak behind them and kill them? Is it more than just "spray bullets nonstop and hope it hits the guy in front of you in a bayonet block"?
I don't know how you expect this to be quantified in a relevant way. Is the skill of the individual rifleman important? Sure. However, you have to consider the different skill requirements for a modern (say WW2 and later) infantryman and an infantryman firing with an unrifled musket. There are a few big differences between the two. Notably the range at which engagements happen and what target the infantryman is expected to fire at.
So, for a modern infantryman you have to be able to consistently hit a target the size of roughly the standard E-type silhouette at ranges of up to 300 meters. Let's say 50x50 cm just for the sake of argument.
For an infantryman carrying an unrifled musket you have to be able to consistently hit a target that is comparatively huge. 2 meters tall or so by 20 meters wide at 100 meters or so. As long as you can hit within that space, you're likely to hit someone in the enemy formation.
So what does this mean? Well, reaching a modern skill cap requires significantly more practice than reaching an unrifled skill cap. Now, a skilled black powder shooter can fairly reliably hit a 50x50 target at 100 yards with a Brown Bess land pattern musket. I'm relatively sure a skilled infantryman in the 18th century could do that too. However, to take his place in the line, he didn't need to.
So where does this leave us? Well, marksmanship is more important today than it was in the 18th century. No denying that. Engagements happen at longer ranges with far more accurate weapons. However, it is uncharitable to compare an infantryman of the line to a modern infantryman. We no longer engage in the kind of warfare that the infantryman of the line from the 18th century trained to excel in.
There is also a question of opportunity cost in the training of a line infantryman. Yes, more time could be spend making the line infantry more accurate. However, it would generally be more beneficial to make the better loaders. Why? Because if they can already reliably hit the enemy formation at their intended range, firing 4 times a minute instead of 3 has a much greater effect on the damage they cause than training them to pick and hit individual targets.
So is volley fire misunderstood? No, not really. It's a pretty inaccurate way to fire. At 100 yards a British company would score around 50% against a formation sized target. Under combat condition, when someone else if firing back at you and the world is covered in acrid smoke it was probably a lot less.