Very simple: Golden Age artists are originals. They're doing things for the first time. (Not everything of course- all artists depend on their predecessors- but a significant number of things.) Hardy for example: Had anyone written realistically about Wessex farm workers before? Don't think so. Hardy's books are full of things that are being seen and described for the first time- from the passing of the seasons on Egdon Moor to the workings of a steam-powered threshing machine. As he says in one of his best poems, he hoped to be remembered as "a man who used to notice such things."
Silver age artists copy. Ishiguro for example. The Remains of the Day is almost entirely constructed out of earlier artworks: Wodehouse, movies of the mid century, sketch shows, sit-coms. Everyone and everything is a stereotype: dozy aristocrats, stiff-necked butlers, Nazis coming out of the woodwork. Even the theme- repression is bad for you- had been worn threadbare by the time Ishiguro took it up.
Golden Age art challenges, Silver Age art reassures.
The Golden Age of the novel ran from approximately 1800 to the 1920s- and came to an end with Ulysses. After that everything that could be done with the form had been done- and later writers were left to rinse and repeat.