Yep. Although I've read a few good posts on Medium, most of the content feels like something you'd find in popular business books. The design of the site seems to discourage anything with a technical/academic/deep thinking side. I've been wanting to post there, but I don't have anything to say that would be a good fit.
Let me place my bet: Professional look (design, typography) + Medium brand + very little effort to publish + chance to get featured if it attracts clicks.
There's an entire subculture of fake "you can do anything" motivational stuff on the web. The purveyors are direct descendants of Tony Robbins and Dale Carnegie and whoever was selling that stuff before him.
I don't think thats necessarily true, but I also think that Medium has that kind of connotation for me.
I think the lack of branding on Medium sites has something to do with it. People ended up lumping everything as "Medium articles", from spammy "growth-hacking" articles to well-researched, well written investigative article.