IMHO, it is the ability to tell a story. If you don’t have an interesting story to tell, and you don’t know how to tell it in an interesting way, it doesn’t matter how ‘good a writer’ you are. If you are that person who doesn’t know how to tell a good joke at a party, you are probably not going to be a successful writer.
So, have an interesting story, and know how to tell it. The rest is just typing.