The article summarizes a study that "confirms [the authors'] hypothesis as well as the community perception that the system was flooded by content that nobody cared about, while really interesting content was getting rarer" and presents this as a problem to be solved.

I think this is actually not a problem, because most users can still successfully find the answers they need on Stack Overflow.

Here's how I believe I and other users use Stack Overflow. We have a problem. We Google that problem (or occasionally search on Stack Overflow). We usually find a fairly popular (and high-quality) question with a fairly popular answer. We're satisfied by that answer.

The article points out that the number of good questions has remained constant, but the number of bad questions has increased. Maybe there's really a close-to-constant number of good, searchable questions that can be asked at any given time, and the declining average quality is just a result of Stack Overflow's popularity.