I'm not certain what statement you're implying, but yes, accessibility of bookwriting has definitely decreased the quality of books.

Even technical books like Hardcore Java: https://www.oreilly.com/library/view/hardcore-java/059600568... are god-awful, and even further away from the seminal texts on computer science that came before.

It does feel like authorship was once heralded in higher esteem than it deserves today.

Seems like people agree: https://www.reddit.com/r/books/comments/18cvy9e/rant_bestsel...