Previously, the default time period for topic listings under the
Activity sort (which is the overall default) was set to 3 days. Part of
the purpose of this was to stop long-lived, off-topic threads from
sitting at the top of the site indefinitely. However, now that the
Activity sort is adjusted to have a way to consider these threads
"uninteresting" and prevent them from bumping, that's no longer
necessary.
We can try Activity/"all time" as the default sorting again, and should
be able to resolve any issues through using the "uninteresting"
judgments instead of trying to use the shorter time period to hide it.