I think two things may have been going on relating to your lack of engagement for these articles.

1. Many people/writers don't understand that there is a SOCIAL element to SOCIAL media and that means interacting. They don't understand the community aspect Medium is trying to create. This is a problem for people writing on traditional blogging platforms, too. Even on Facebook I see a lot of writers using it as an announcement page and not interacting with others.

2. People are overwhelmed by the huge amount of material to read on Medium and the Internet in general. The push to publish on Medium may keep writers here from keeping up with other aspects of the site, like engagement.