In Dune most of the narration follows a protagonist that navigates the world. In A Song of Ice & Fire there is not a single protagonist. There are multiple characters that are elevated to the same level of importance. Covering world events from each point of view requires more pages. Having multiple characters that are the same level of importance is one of the hallmarks of the series. When starting to read the series a person is usually told that they will not be able to predict who will die. This is a key element of the story telling process.
A Song of Ice and Fire has more named minor characters and a wider range of named minor characters. In my opinion this makes the world more rich and represents a deep understanding of the entire society. Dune deals primarily (99% or more) with aristocrats and their servants/warriors. A Song of Ice and Fire will talk about everyone from Kings to poor fisherman.
I find the older the book, the slower and more waffly (if you want to be uncharitable) its prose. I haven't looked into this at all, but it always feels to me like editors are a new edition to the writing process.
Ironically I usually really enjoy the actual prose they wrote, because it's often beautiful, but after dozens and dozens of pages of hearing about how pious some bishop is you have no context for you really start to wish Victor Hugo would just move the fuck on.
In some cases older writers were actually paid per word. Dickens comes to mind.
Our aesthetics have changed, that is for sure.
For what it's worth, in SF & Fantasy short fiction is still hanging in there:
http://clarkesworldmagazine.com http://dailysciencefiction.com http://www.analogsf.com
You're the second person I see in this thread complaining that texts have become too bloated and using this exact example. Perhaps the guy is just a hack.
In terms of bloat, excluding the Tale of Genji or the Story of the Stone, I can hardly think of anything in the 1800s that pushes into the 1M+ word mark in order to tell a complete story. I mean, people used to joke about War & Peace being long and it's hovering around 1/2 a million words -- and at least when I read it, Tolstoy seemed to be using every last one of them.