Hmmm.....
I think there's lots of "common knowledge" anachronistic criticism of 19th C tactics, to wit: "They just stood in lines and shot at each other!" without considering the alternatives.
In large scale combat, one side gained the field by pressuring the other side to retire. This was a result of mass, not precision accuracy.
The myth of the American rifleman taking out entire British lines is -- a myth. In open combat those "stupid" lines rolled over American superior accuracy over and over.
The Boer war did portend many 20th C "improvements" to tactics -- concentration camps, targeted strikes, mobile units, and civilian control, for starters.
But the Civil War had its share of innovations.
Tacticians have to be conservative -- they can look back on engagements and prove "This works!" The innovation hasn't been tested yet and is therefore risky.
Rommel was Germany's foremost tactician. yet in Attacks! he wrote that the soldier's best weapon is the shovel. This from the ace of fluid, mobile land warfare.
No doubt about any of that whatsoever - what you've written is completely accurate.
Yet, and I might be completely missing your point, are you suggesting that it was acceptable to fight the First World War, under any standard that we might apply, in the way that it was fought right up until the last German offensive?
I'm not criticizing 19th century tactics, as they were used in the 19th century. While I'm not sure that we can say there were always clear winners, there were always clear losers. Yet, the writing was on the wall even fairly early in the war. What happened in the Civil War, though in many instances was utter insanity, is far different from what happened in the First World War.
It's one thing for one massed formation to charge an opposing massed formation - dug in or not - when both sides' weapons are kind-of-accurate, at best, at ~150 yards, and they've only got one shot.
It's another thing to pull a Pickett's Charge in the face of an enemy that has
rifles that pretty-stinking-accurate, in the hands of an average shot, to ~400 yards. Not to mention the great advances in artillery that were made. Now, was that known in the Civil War? No, at least not at the beginning; and both sides had some varying degrees of success despite the seemingly small changes in technology, thus reinforcing the methods used. But they eventually learned. Some more quickly than others.
Look at how the Civil War ended up. Petersburg. A battle of attrition, because even though outnumbered, the defense had the clear advantage with the technology of the day. Until the supply lines were cut, at least.
So, my criticism isn't really directed at the Civil War. They worked with what they knew. Which, in turn, led to new developments.
My criticism is directed at the fools - and there is no other description for it - who didn't learn from what happened in the Civil War and elsewhere.
In my eyes, and this is of course only my opinion, that failure was
inexcusable.