The language of Tolstoy and Dostoevsky sounds just as archaic to Russian readers as Victorian English does to you. In a sense, preserving this archaism is closer to the original than trying to modernise it
But it wouldn't have sounded archaic to a contemporaneous russian reader. So the translator's choice is to translate into modern english, as the original audience would have experienced it as modern russian for their time. Or to attempt to recreate a modern russian audience's sense of archaism in english. It's an artistic choice, neither is approach is inherently better than the other.
