Well FWIW I know a few writers who have really good publishing deals, a few more who have agents and are subbing to publishers, some more who are subbing to agents, and some who haven’t got to that stage yet. The honest truth is that the vast majority of writers I know well are bloody good. The ones who have the great deals are bloody good, but so are the others. It’s just that the ones who are farther along are farther along. I know many superb writers. The ones who aren’t published aren’t objectively less good than the ones who are.
The one thing I have noticed about the people who have managed to succeed at each step of the way are determined. They’ve had setbacks and have picked themselves up and gone on. They’ve tried with one book, failed, written another, tried again, failed. Tried again. Mostly they’ve just been at it longer.
I honestly believe that for the most part, talent + persistence = success. There doesn’t seem to be any pattern to the time it might take, but nothing I’ve seen in this business causes me to doubt that a fundamentally talented writer won’t succeed sooner or later.