I've been meaning to post this question for a while, but only now got around to it. Over the last year or two, it has been my observation that a) the rate of (good) new questions has decreased noticeably and b) questions have been closed much more quickly as off-topic. (The first is borne out by the site stats on https://area51.stackexchange.com/proposals/28815/computational-science -- although the mods might have access to more detailed site analytics than I as a 10k+ user -- while the second is personal observation, including my own behavior.)
I suspect a link between the two. Assuming we wish to grow our community (which is not a foregone conclusion, and may be argued here), do we wish to revisit our off-topic policy to make it more inclusive?
My own personal opinion -- which I'll detail in an answer below to be voted on -- is that for a site of our size, we don't have much to gain by being exclusive (and much more to gain by gaining a reputation for being welcoming like https://tex.stackexchange.com, which I hold as a model community on the internet), and restricting our scope to have no overlap with other sites would not leave a viable community. I would therefore appeal to voters to spend some time considering whether the question is really irredeemably off topic before casting their vote. (And I do not exempt myself here -- I noticed that I have gotten much more trigger-happy over time; in fact, this observation is what prompted this post.)