This might be a bit contrarian, but I don't really think anyone involved with Stack Overflow (the company or community) are really in a position to come up better solutions to why people aren't using the site. The simple reason for this is that we are already vested in the site and culture and don't really have any perspective on why people aren't using it. This is also why I think that "The Loop" will really only be useful for addressing issues that the existing community is facing (ex., UI/UX, moderation, content contribution).
Outside of the user and maintainer base there are likely three groups of people:
- Former users of Stack Overflow that no longer use it.
- Potential users of Stack Overflow who are passively aware of the site, but aren't registered or contributors.
- People for whom Stack Overflow is largely irrelevant.
With regards to the third group, these are people for whom there is nothing Stack Overflow can do to attract them. They may stumble across the site, but since they aren't involved with programming in anyway, it's of no value to them. Net result, there is not much point in focusing on them, baring promoting other network sites.
The second group is a bit more complicated in that these are "drive-by users" that will use and consume the content but may or may not see the value in registering and contributing. While these users can be targeted via surveys, it is also difficult to get them since you are so dependent upon convenience sampling that your results may not be representative. Where Stack Overflow wishes to go with this group is going to be quite complicated and driven by their internal corporate goals, but attracting people is quite complicated.
The first group seems to be the one that is driving most of the discussion that we see. I suspect that Stack Overflow might be privy to some data that we do not have (ex., users sending them an email before leaving the site) or they are following why moderators were leaving. That being said, why people are leaving could be for a lot of different reasons ranging from professional (ex., career change, retirement) to personal due to the community. Depending on why people leave they may or may not be passively active on Stack Overflow or another network site. For example, despite being a private beta tester on Stack Overflow I'm not very active on the site any more, largely due to a career change. Due to my depth of knowledge I might be useful as someone to answer questions, but I'm not much of a Jon Skeet.
You will note that I focused much of this analysis on Stack Overflow and that's because I suspect the company is doing the same. The second most popular site on the network, Super User only has 834k users compared to 11m for Stack Overflow. Things drop quickly after that and I'm guessing that most network users come from Stack Overflow. Personally I think this focus on Stack Overflow is a mistake since I suspect that the user base has likely plateaued. Consider the following:
According to Evans Data Corporation, there were 23 million software
developers in 2018, this number is expected to reach 26,4 million by
the end of 2019 and 27,7 million by 2023.
If the 26.4m estimate is correct then Stack Overflow has roughly 42% of the world's professional software developers. To put this in context, Facebook has 2.45 billion active users which is about 32% of the world's population (their target user base). While Stack Overflow says their target user base to be "anyone that writes code" I'm not really convinced that you are going to get most of them as registered users. Case and point, in my professional community I know a number of people who write code and will occasionally look things up on Stack Overflow, but don't see the point in asking questions since the answers are already there, or the active user base is on a listserv.
As such, I think Stack Overflow is trying to change directions a bit, but it needs to put less focus on programming (i.e., Stack Overflow and affiliated network sites) and more focus on building the features and user base to support other sites like Arqade (148k users) Personal Finance & Money (64k users), or Worldbuilding (58k users) to name a few. When you consider how many people play videogames, it's shocking that there are only 148k users on the site - why is that the case?
So in summary, I think Stack Overflow as a company really needs to start thinking about other network sites as opposed to just Stack Overflow and affiliated network sites. If you can only get 148k users on a Q&A website about video games, then you need to be asking the fundamental question of why people aren't using it. Stack Overflow in and of itself has likely plateaued and their isn't much growth potential no matter how much the company or community tries look for solutions.