Although it's about five years old at this point, Ann Hadley's book "Everybody Writes" still resonates--as much for how to devise a content strategy as it is for a mentality for marketers today.
In many places I've had the opportunity to work, much of the "writing" is outsourced to agencies and contractors, with the "manager" collecting all the finished product and loading it into the bill of materials--at least that's how it used to be for me.
But once I started to write, and once I insisted that my team not only manage an agency but be able to write the copy, the blog, the ebook, the social media post themselves, I got much closer to my marketing. I had to articulate a true value proposition for a web page; I had to write posts that were interesting and engaging (like this one is, I'm sure!).
The point is that by writing you start to see things from the customer point of view--you go through the process of taking someone you don't know on a journey with you to hopefully want to learn more about your product or service. And most importantly, you feel that sense of pride and accomplishment when you're the one that did the work, not someone you hired.
Even in this digital world writing is good for marketers--make sure you and your team take it seriously--it will be reflected in your results, and how you represent your product and company.