The user experience of the people in the 1% (the 90-9-1 rule - https://en.wikipedia.org/wiki/1%25_rule ) is diminishing. Existing systems showing their age and failing to scale, processes and norms that work in tandem between technology and people are straining as times change.

In these cases, the technology needs to keep pace with the systems (both computer systems and people systems) that it supports. Failure to do that means that the people who are creating content are having to expend more effort to make up for it.

Be it people leaving, or needing to spend more effort to attain the same quality - the result is the same. The quality of the site (questions and answers) is diminishing as people are less able to provide good answers and curate existing material to make good content more visible.