Eh, I disagree. I mean sure there is tons of bad stuff, but keep in mind that writing is more open than even now with the interwebz. It goes without saying that the ratio becomes a bit fucked with that. There is still some great stuff being published.Here’s a decent article as to why modern literature, especially Young Adult, sucks for the most part:
YA has gone down tho, but then again, it was always bad. After all, YA was never meant to be deeply intellectual in the first place. It's emotional masturbation for the most part.
At the same time, Haruki Murakami is pretty YA'ish and his work is top notch. Not entirely sure if his work counts as YA tho, but it's definitely aimed at that crowd with some of his work.
At the end of the day, there has always been few good writers. On top of that, most intellectual writers don't get recognized for decades most of the time. Nowadays a lot of writers want to provide for themselves so putting out some trash is usually the way to do it.
In my opinion a lot of this stems from the media and "critics" that trash anything original. If you try something new and a bit "odd" you get trashed and won't receive any hype. Write something LBTQ or some trash like JK Rowling and you'll get tons of aid from the mass media. Critics will still burn you tho, those cunts don't like anything that isn't Kafka.