The idea that any single default can possibly be considered high quality for tens of millions of users is unrealistic. That's like going to a grocery store, asking for a "default shopping cart," and hoping its contents will be suitable for you.
The default shopping cart is probably much closer to my taste than default reading material would be.
Although, now I come to think of it, for years we did have default reading material, it was called a mass-market newspaper, and it wasn't all that bad. Newspapers are very readable and fairly sensible, content-wise, compared to something like reddit, because they're carefully designed by a small group of people to appeal to a broad cross-section, whereas the dynamics of social news sites tend to push shiny junk to the top.
A newspaper is like a default shopping cart which contains meat, vegetables, eggs, milk, bread, and rice. Not all of it is to everyone's taste, but if it arrived at my door every week I wouldn't die of malnutrition. Reddit is like a default shopping cart constructed by polling a thousand teenagers on their favourite foods; it contains twinkies, cognac, Junior Mints, bacon, Twizzlers and beer.
> it was called a mass-market newspaper, and it wasn't all that bad.
I actually doubt that. Sure, there were social advantages to having a smaller body of reading material that most literate people had read. But the Internet allows us to do two different but important things: truly democratize editorship (like reddit), and enable niche editors to easily distribute their content (like slashdot, slashfilm, or techcrunch).
Doesn't stop the fact that I'd get more satisfaction out of reading the New York Times (or even the New York Post) than browsing the front page of reddit.
Oh look, a picture of a velociraptor with a caption. And someone's cat. A terribly-drawn cartoon about why console gaming is better than PC gaming. Someone else's cat. Another cat. I'VE SEEN CATS BEFORE, PEOPLE!