Christmas Carol is thoroughly modern. The battle between the lords of finance and the wage slaves is still being fought, with each side laying claim to having the just cause. Witness the current US presidential election--it's disconcerting that economic thought can still be rooted in Adam Smith and Malthus. We have learned nothing in 150 years.
I think the biggest difference to a modern sensibility is that Scrooge is clearly damaged by his unfortunate childhood and his avarice is an attempt to compensate for the love he didn't receive. We can regard him with a modicum of sympathy and understanding, the more so since he doesn't live well off his greed. The Cratchits probably eat as well and live as warmly. The numbers in his ledgers drive him--and who's to benefit when he's gone, also? There's no point to his greed. Contrast that to the robber barons and aristocrats of yesterday and today. I think Dickens pulled his punch on that one. The upshot of the spirits' visits is not only that the poor and disadvantaged will benefit from Scrooge's generosity, but that Scrooge himself will benefit materially as well as spiritually and emotionally. I don't remember specifically, but don't Scrooge and Tiny Tim die at roughly the same time? Scrooge manages to stave off his own death as well. It's a double pay-off; he's redeemed when it comes to judgment at death, but he also gets to enjoy and prolong his physical life. Win/win.