I think that a case can be made for ignorance being one of the major themes of the work. Scrooge only comes to his revelation after his spiritual visit. Once this is made clear to him, Scrooge emerges out of ignorance to understand what he must do and what he must avoid. His ignorance is what kept him in the emotionally frigid state in which he lived. Dickens' point being that once individuals are aware, they will act in accordance to more elevated notions of the good. When ignorance appears inside the robes of The Ghost of Christmas Present, a warning is issued, elevating the role of ignorance in the thematic understanding of the text:
This boy is Ignorance. This girl is Want. Beware them both, and all of their degree; but most of all beware this boy, for on his brow I see that written which is Doom, unless the writing be erased.
The idea that if an individual is aware of the challenges in ignorance and warned against them in the present that they can initiate positive change is a major force in the work. I think that ignorance can be seen as one of the many themes of the work that speaks to its power and its ultimately redemptive qualities.