Writing is without a doubt a learned talent.
Stupidity and laziness, however, are almost always natural and are usually capable of completely overwhelming good writing potential.
In other words, learning to write is easy. But some people don't hone their craft. People who search for the magick formula of Good Writing tend to fall into this category.
But seriously, there's nothing easier than learning how to write. You just have to work at it, a lot. That's too much for most people. They just want a button to press so they can become Stephen King and J.K. Rowling so they can make a billion dollars and go back to watching TV. It just doesn't work that way.
The idea that some people are just born this way or that way isn't just insulting, it's completely not true. If you want to be accurately specific, you could say that some things are learned through natural development depending on your environment growing up while other things you have to learn by seeking them out and very specifically trying to gain some skill in it. In that area I'd have to say that some people are simply raised in a more creatively-nurturing environment than others, and while that might make them more of a "natural" storyteller, they weren't born with that quality, you see what I'm saying? And even the so-called "naturals" had to work at it, a lot. Anyone who tells you differently is either: A. Lying to you, B. Lying to themselves, or C. Both.