Facebook claims that the decision on how to change the algorithm was taken following indications coming from the users through their Feed Quality Program.  News Feed rankings will learn from past user behavior and take into account the time spent reading stories after clicking through on a piece of news, whether it is an Instant Article or an article in the mobile web browser.
 
What Facebook learned from their users surveys is that "the actions people take on Facebook—liking, clicking, commenting or sharing a post—don’t always tell (...) the whole story of what is most meaningful to them” and that "there are stories people don’t like or comment on that they still want to see, such as articles about a serious current event, or sad news from a friend".