“And here we found the culprit. The paper I was submitting belongs under cs.CY, Computers and Society, as I now know after reviewing all the categories more carefully.” I’d think the indirect cause is ai, given its recent bull/glass shop approach.
Within the cs.CY category, I only found a slight increase in delays since 2016, that seems to be well within error bars, but it could also be that my sample size was too small.