Over the years, I have spent a fair bit of time on Stack Overflow and other Stack Exchange sites (at the moment, 816 answers and 70 questions, across the sites), in many of the sites from their early days. What I find happening on multiple sites, repeatedly, is similar to what I've seen on many other online communities like Wikipedia etc:
1. It starts as a community of people eager to share their knowledge, help people, etc.
2. Initially, the small community of users scours every (or a large fraction of) new questions that come in, jumping at opportunities to help (and perhaps also demonstrate their expertise etc: it feels good to answer a question well, like disposing off a level of a video game or whatever).
3. Over time, as many users come in, the community develops its own norms of what's good and bad, its own in-jokes and in-group markers / shibboleths, etc.
4. At some point, the number of new user actions that come into view becomes too much for one user to manage. Somewhat overwhelmed, and given their overdeveloped “connoisseur” tendencies at distinguishing between good and bad questions (https://xkcd.com/915/), they tend to look for shortcuts to dispose of questions (“this question is bad because ____”). Any question that does not match the in-group standards of a good question can easily be disposed off instead of engaging with them. It is easy to forget that these standards are somewhat arbitrary, and often not even encoded well anywhere... and even if they were, new users won't read it anyway. It is also easy to forget one's original motivation and purpose, of helping others.
The end result is that new users asking their questions in what way seems natural to them (remember Sturgeon's law) almost uniformly have a bad experience, though from the perspective of the regular answerers of the site, they are continuing to answer good questions at the same rate.
I have not had a bad experience asking my questions; I'm pretty sure I can still go to one of these sites, ask a question, and have it be well-received, but that's because I know the norms, the superficial things that make a question look like a good question “worthy” of being answered. But whenever I look at say Stack Overflow (the oldest, biggest site, and by far the worst offender in this regard), I see many horrifying instances of a new user's question being “rejected” for trivial reasons, when in the old days we'd have helped the asker improve the question and worked harder to extract the “pearl” inside the question.
(My last phrase reminded me of the title of a post from 2011: https://stackoverflow.blog/2011/06/13/optimizing-for-pearls-... which ends with:
> Therefore, the only logical thing to do is to maximize the happiness and enjoyment of answerers. If this means aggressively downvoting or closing unworthy and uninteresting questions, so be it.
I think this was the right choice to make at the time, and if Stack Exchange Inc in order to make the sites more welcoming ends up making the sites a less fun place for answerers there won't be much of value left, but still there's a lot that can be done to understand why otherwise initially well-intentioned answerers end up behaving this way over the course of years, and finding ways to keep answerers on the site without regularly crushing those seeking answers.)