A lot of marketing blog posts are filler. I think this is because it takes time to do deep research to uncover the concrete facts and examples needed to write influential content.
I suspect the reason lots of writers don’t take the time to do this is because most content writers are effectively paid by the word, even though most people price jobs on a project basis. Client’s want the most value. And freelancers want to keep their prices down to be competitive. It’s a negative cycle.
I think the solution is to understand that, as always, quality is much more important than quantity.
In truth, there are some publishers who get this, and plenty who don’t. So there’s a mindshift required if clients are to reach their full growth potential through content marketing.