Agreed. This related to the misconception that "little or no activity on an open source project means that it's dead." That statement is frequently true, but not always.

If most of the common questions have been answered, then there will obviously be a correlated decline in the number of questions posted and subsequently answers posted. Esoteric questions aren't abundant, especially over a constant time frame.

Declining question/answer activity shows that the website is healthy. I've opened S/O a few times over the past year with the intention to answer questions, only to find duplicate/off-topic/low-effort/etc. questions.