Actually not that good, when you realize that they are/were right about that in both eras.
Not much has appeared since 1945 that really is comparable to the "golden age of literature" (that would be around 18xx-1940, I guess) --just a few exceptions to prove the rule, and tons of crap.
Your "golden age" also had an overwhelming volume of crap that no one cares about that got published then too. The idea that nothing good gets published now is older than you think. In the 1700s people would say the same thing citing no one has published anything great since the Greeks and Romans. Amazing art is always being produced in all genres, at all times. You may not ever find it but it is out there, somewhere. It is getting harder to find amazing art now because of the volume of humanity's creative output has been going up exponentially with industrialization (for various symptomatic reasons).
Try and find something new. Don't wait for someone else to tell you what you should read because they said it was great. Find your own great works.
In Orlando, there is a recurring character throughout the ages, a poet which is always complaining that nothing of value is created nowadays. In the seventeenth century nothing of value have been written since antiquity, in the eighteenth century nothing of value have been written since Shakespeare and so on.
"""In whose 'literary' eyes is 1984 a minor work? It's an important piece in the 20th C. literary canon."""
It mostly has political (in the broad sense) importance, not actual literary one. ("Brave New World" is even worse in this regard, but it also has the same kind of importance).
"""And you've completely discounted the post-modern literature of post-WWII, including Nabokov (!), DeLillo, Franzen, Morrison."""
I said there are "a few exceptions to prove the rule". Nabokov could be one, true, but surely not DeLillo, Franzen and Morrison, and not crap like Rothman, Pynchon et al.
Obviously listing a bunch of names isn't going to prove the argument one way or the other, but I think it's a bit unfair to claim that all post-WWII literature is crap mod a few exceptions. Sci-Fi basically didn't exist before 1940.
I think it is more relevant to look at the 19th century vs. 20th century.
Um, seriously? What genre would you place either of The War of the Worlds or 20,000 Leagues under the Sea, then? That the books manage to get a lot of things wrong doesn't really alter the fact that they were early, very popular examples of science fiction (and there were a lot more dating back to before WWII, when SF really took off.)
Not to mention a little known author going by the name of Rowlings. I've read a lot of books, but I've never seen such an indepth treatment of racism as you find in the Harry Potter books.
I don't think you can really compare the last 50 years (anything more recent and it's really hard to judge how 'great' an author will be) with a 150 year period. Especially when you are including the Lost Generation which was, frankly, contemporary in 1945. Hemingway hadn't even published "The Old Man and the Sea" at that point.
It's good to think that in 1945, just as now, people felt that the golden age of literature was behind us.