It should be obvious that plagiarism is out of the question. But covering the same topic as another website or putting someone else's thoughts into new words can be just as bad. If you want to stand out in the world of search engines, you have to come up with new ideas and cover topics that haven't been touched on yet. If you can find 10 competitors, all of whom have a very similar post already, it may not be worth publishing your work.
Validation/credibility. Are you validating your claims in the article? How credible are your australia mobile number list free sources? Linking to other high-quality articles is a good way to corroborate some of your claims, especially if you cite specific figures. It's also important to establish your own credibility as an author over time; the more editors work with you and the more links you have pointing to your website, the more authoritative you'll be seen as.
High-quality content also doesn't have technical issues. I'm not talking about technical SEO here; instead, I'm talking about technical issues with how the content loads or how people interact with the content. If it doesn't work on certain mobile devices, or if it's structurally difficult to read because of the way it's formatted, you're going to experience significant problems.
There's nothing wrong with producing as much content as you can; in fact, there are many advantages to having a larger body of content to work with. Most importantly, quality should always be your top priority, outweighing quantity in the process.