Quantity has a quality (or lack thereof) all its own.

How many shit books can or will you wade through to find a good one? Particularly when some percentage of the shit ones are "good enough" that you won't necessarily know it was shit until after you've read some or all of it? What do you do when the ratio of shit to good is 100:1 or 10,000:1? In the past, you could find a trusted publisher or reviewer without too much trouble. Soon, if not already, the publisher and the reviewers will have the same dross ratio as the books do.