In my opinion you are correcT on all counts.I had not noticed the lack of new regiments mustering please tell us what you find...

Patriotism fueled the fire in 1961=62.Lincoln's call for men caused fever but even in the fall of 1862 enlistment, that fever, was breaking.One just has to look at conscription/draft laws of both sides 1862=63.Horror;Casualties including maimed in the tens of thousands were coming home, many not at all.What was thought to be short lived Rebellion at first proved to be dug in for the long haul with no end in sight.

Your second point also has merit.Not an Wisc. regiment my GGGrandfather was transfered to Recruiting service (Camps Yates and Butler,IL.)and funneled over twenty-five thousand men to existing regiments as replacements for the Army of the Cumberland May 1863 till Jan. of 1864.However even those might not be as eager as I have orders looking for a man my GGGrandfather recuited mustered but, didn't show up around the time of Chickamuanga,some say one of the bloodiest two days in history.

Third if you mean war fought with honor as a thing of the past and Grant's policy of "Attrition" along with Sherman's "Scorched Earth" as modern .Then, yes the way war was fought changed.
I do feel it took years off the war in the long run..but something was lost in the process.

Again let us know..