The myth that writing is a skill that one is either "born with" or not is inherently false. Writing can be taught; more to the point, how to write effectively can be taught. One reason that many professionals don't write well is that they simply lack the necessary tools. For instance, many workplace professionals use one or two "strategies" (outlining is a common one) when writing, even if those strategies don't result in well-written documents. And they use these one or two strategies because they haven't been taught about other methodologies that will impact their writing while making the writing process easier for them.
One simple strategy is practice. Just as we practice if we're learning a musical instrument (or even if we've mastered that instrument), spending time practicing is an integral part of mastering the skill of writing. There are many effective techniques available to do this practicing that take less than 15 minutes a day. And research shows us that 15 minutes a day practicing is all that's necessary; you don't need to spend hours and hours. Think about it: most of us probably feel that we're fairly adept at communicating orally, right? We don't fret about seeing our colleagues in the workplace and worrying what we might say when they ask us how we're doing or what we did last night. Why? Because speaking is part of our everyday life. In other words, it's a form of communication that we practice every day, all day, without thinking twice about it.
Writing is often problematic for professionals because they make it problematic. Professionals don't practice and, worse, often don't view writing as part of their jobs; rather, many professionals view writing, whether it's a report, a memo, or an email, as secondary to their jobs, and that creates problems. Because of this mindset, they procrastinate, which often means that what they produce isn't well done, or they resort to "modeling," which means that they use versions of another document that they think (hope or believe) will fit the bill. Both of these "strategies" can work to ensure that the writing that is produced lacks an obvious purpose and audience and is disorganized and verbose. We see these as common practices in many of the companies we teach workshops for.
When professionals are provided the necessary tools and opportunities to learn how to improve their writing, they can streamline their writing process and write documents that make the point quickly and succinctly. The lack of tools, or strategies, cause so many professionals to be less than stellar writers. And useful tools are available, such as research on how readers read and how readers make sense of information, that writers can use to great advantage in their writing. And these tools are, in many cases, easy to implement, but professionals don't know about them.
So, back to the original question: can writing be taught? Yes, it can. All professionals need are the right tools and knowledge to write impactful, compelling documents.