This has existed for at least two years: https://www.duolingo.com/stories
Yes, it does not cover every language but the intent is to address that ( perceived ) complaint.
I disagree that an actual coursebook is more helpful.
I used Duo for 6 months prior to moving to a Germany. It gave me an incredible confidence boost to be able to at least understand what was going on around me.
After living in Berlin for 6 months I did a course and I was far ahead of others who had taken formal courses before.
It has been 2 years since I left Germany, I still do my Duo daily and have continued doing German courses.
It has helped maintain my minimal ability.
> it also likely depends on person
Indeed. My partner at the time did the same as me and Duo did not work for her at all.