What's good about Doctorow's The March and what's missing

Figuring out a little more about the structure of E.L. Doctorow's The March as I read further, and I see now that we will follow several strands of narrative in roughly alternating chapters - and it may be that the narratives overlap and entwine further into the novel. I don't have all the narrative strands clear in my mind yet, but the three that Doctorow has developed the most so far are: Pearl, the half-white slave teenage girl left more or less abandoned in the attic (she's shunned by both cultures) after the plantation owners free the slaves and flee ahead of Sherman's army - rescued by an officer in the army, treated kindly (others suspect he's made her his concubine, but they come to see that he's protecting her) - surprisingly, he dies in ambush - Pearl will clearly continue to be a main character, a bridge between cultures; the daughter of Georgia Supreme Court Justice who goes off with the union doctor, working beside him as a nurse-attendant, after her town is ransacked and her father dies in his sleep - strangely, another narrative strand about a chaste, somewhat protective relationship between man and woman of different cultures. A third strand is about two Confederate soldiers who deserted, were arrested for desertion, wriggled to freedom, and now kind of bounce back and forth between the two armies, struggling in a comic-opera manner for sustenance and survival. Each of these story lines, and some others not yet developed, told beautifully, with a real sense of life during time of war, the constant terror and uncertainty and danger. I am surprised, though, at how little, so far, ELD has to say about the slaves and the freed slaves: it's as if the whole reason for the war is forgotten; I'm also surprised at how much he tries to build our sympathies for the white Southerners whose lives are upended by Sherman's army, about which I only have to say: upended from what? How did they manage to live in such luxury and abundance in the first place?