Hmmmm, I think you hit the nail on the head in your first sentence. "Reader interest", I write on a lot of different topics. And I get various interaction from different readers for different topics. For example, My poetry and stories about writing get more views than when I write about Lego and video games - the latter getting on average 10 to 15 views. I think the major issue is, I am not catering to my audience, I am not always writing stories that pique the interest of those that follow me.
2. Not all 400 odd followers are always active on Medium. Some come and go and others read almost every story. It's the same with youtube subscribers and views. I'm just happy a few people enjoy it.
3. I think visibility on Medium is very hard for writers like me. I don't think I have much luck being shared by the algorithm because my writing is never curated. Probably because they are not up to the standards that are expected.
4. Social media is a puzzle I don't think I can solve. If you can interact and engage with a lot of people and grow your followers then there are more eyes on your story. For example, if you had 10k followers, you can be sure that at least 1000 people will click on your story. But, I only have 10 odd follows and I don't use Twitter or FB at all.
Those are the problems I think I have.
For the next step, I think publishing on Big publications with lots of followers might help. It will increase the chances your article will be seen and read. Try pubs like PS I love you, Ascent and others like that.
For me, I have had steady growth in the past 4 months. Not an explosion of success like some writers who instantly get curated and get 1k follows in a few weeks. I'm like a slug compared to them. But I'm taking it at my pace. Slowly growing one story a day.