I guess the answer to some degree is "it depends." I like both Hugo and Dickens, and I don't think there's one inherent form a novel needs to take (Tristram Shandy for example) to be a novel. It's also worth remembering that Dickens wrote his book as a serial published in pieces, while Hugo wrote his as one large work. I'm not sure Dickens could have afforded the kind of digressions Hugo took.

(Another digression-heavy writer who comes to mind is Melville, of course. Moby Dick would be half it's length if it just focused on the story and characters.)

I do appreciate any classic writer who essentially educates me about their world, from Austen to Dumas.