In my experience, curation doesn't really assure that you will gain visibility. It's directly proportional to three key things.
1. Good SEO and Keyword Optimization
2. Topic, and Publication Relevance
3. What you write is actually engaging that people read it from the start till the end and vice-versa.
Overall, I have been curated, but that doesn't really assure visibility.
Constant refining and writing will inadvertently help you to gain visibility everyday, and at times whenever you post a story it might be shared with the internal traffic on medium without even being curated, so it highly depends on what you write.
Perhaps, it's the recommender system of medium that really optimizes your story to help it reach many readers.
Overall, a good read indeed.