> The same thing is happening to Wikipedia, BTW, which is also aggressively moderated

[citation needed]

Well here it is, and you're wrong: https://en.wikipedia.org/wiki/Wikipedia:Statistics

The article creation and edits curves are stable. The former growing at a slightly declining pace, which is expected since the amount of knowledge is finite. The latter is literally flat.

The monthly page views are in decline on mobile (from ~5.7 billions at the peak in 2024 to 4.5 billions currently). They are stable YoY on desktop at ~3.7 billions, and have been rising in the recent months.

StackOverflow is dead, the WP community is thriving, even if the page views have declined a bit.

SO had a moat because of its mass, but the place was a cesspool.