I disagree. You don't get better at something by just doing it a lot. You get better by doing something, evaluating how well you did (on a short feedback loop), then repeat a lot. Just doing and hoping that somehow you'll automatically evolve in the right direction won't get you anywhere. Coding implicitly has such a feedback loop. At the most basic level, your compiler will tell you about syntax. At a slightly higher level, you can see if your code does what you think it does. At a higher level still, in a matter of weeks or months you'll find out about your design decisions and architecture skills.
When writing, you don't get any such feedback. If you're very lucky and you write on quite straightforward topics like API docs, you can ask your readers 'did you get from this what you needed'. For anything more abstract, your readers most likely are not even qualified to assess how good your writing is. Overall, I strongly disagree with your notion that you should just start writing a lot and hoping for the best.