Is there really a plague of bloggers peddling motivational advice as a magic formula to make you a successful writer?
Not sure it's a plague, but the last two motivational types I read insisted a blog is essential to your marketing strategy. In other words, marketing was part of their motivational pitch. In their words, "You can sell more books with a blog."
That said, she distinguished between blogging and writing fiction, although ended up by saying if you want to write, write. She'd already said your chances of making money with your fiction depended more on circumstances that had no direct relation to the quality of your prose.
I just did a couple of spur-of-the-moment images of my sister and her partner, not trying for formal portraits. They're not bad. He thanked me and said they'd use them for their [book] jacket photos. I told him to get writing, already, although for all I know he's already got a draft. I doubt she does.
In other words, writing makes one a writer. Period. (Although of course acquiring all the accoutrements—pens, paper, the right chair, the right desk, the right corner of the house or garden, garret not required—is a lot of fun, too.)