I think the main criterion is length, whether or not there's a real person deciding. My short pieces about music never get distributed (nor is that my goal for them), but a longer article that consisted mainly of the lyrics to a song did. If there is an eventual human judge, my guess is that only articles of a certain length get sent to that person.

Even so, I doubt there is enough staff to read each article thoughtfully and then assign distribution (such a plan would probably bankrupt the site); most sites either use peer reviewing or require a submission fee. I'm not complaining about that premise. The writer has primary responsibility for audience-building. The criteria you list here are a good way to do that, but as with any subjective effort, there are no guarantees that any particular strategy will work.