I believe that writing is simple. Now you might think this is because I have been teaching it for 17 years, but truly I believe that writing is not difficult for a few reasons. Firstly, writing adheres to a structure in some of the same ways as math and science do. There is a process and path to follow. It doesn't have to complicated with separate books, workshops, and courses. It can be straight-forward and even predictable. Secondly, writing uses your inherent God-given creativity. Yes, even when one is tasked with writing an essay, it can be very interesting. It's all about word choice and personality (voice). While you use a pattern to structure the essay, what you bring to the essay makes it unique and hopefully engaging. Lastly, writing is organic. You already know a lot about writing from learning to speak. You know when something just doesn't sound right. You may not know the exact grammar rule that defines this, but you have a sense of language. This will always serve you well.
So, this is what the Writing Garden is built on. (Well these things and a few others that I will save for another day.)