Go and read some random popular fiction from a century ago: the standard of writing is, overall, poorer than an equivalent sampling from fifty years ago, or today. And this isn't just a fashion judgement: we've learned a lot about the making of a solid work of fiction, and we're writing for an audience who have grown up with more sophisticated works of fiction as well.
Whereas the classics are classics because they were the first attempt.
Let me put it another way: compare two aircraft -- the Wright Flyer and an Airbus A380-800 super-jumbo. Separated by a century, the A380 is clearly a more sophisticated machine. Its fuselage alone is longer than the Wright Flyer's first powered hop; it can carry about a thousand times the payload for about a thousand times the distance at ten to fifteen times the speed. But that doesn't in any way invalidate the significance of the Wright Flyer of 1903, does it? Because the WF was the first no-shit heavier than air plane with controllable three-axis flight surfaces, wings designed with the aid of a wind tunnel, and an internal combustion power plant.
Folks who carp at the classics because they don't display the fully-developed characteristics of a good work of modern fiction are like someone who visits the Smithsonian, looks at the Wright Flyer, and decides it's no good because it didn't have a cabin trolley service."
-- Charlie Stross