Agreed, blog posts and open source projects can be just as helpful as journal-published articles. I didn't intend publications to mean only academic journals.
The problem is that many academics are not aware of anything outside the academic journals, and thus work on "unsolved" problems that already have well known solutions in industry.
I didn't think that's what you intended, but in the quote you included, the author is specifically lamenting the lack of knowledge of things published outside academic journals, not the lack of knowledge of things that aren't published anywhere.
