Exactly! In my community I have the « advantage » that people are joining because of a sick pet, and (given Facebook and the community topic) one can assume their digital literacy is low. So I can reach out saying « hope everything is ok with your pet, did you leave by mistake, in case anything went wrong for you in our community do let me know » — but not all contexts have that kind of relational lever.
This is why, imho, user research with non-users or naive users is so crucial to gathering feedback on tool functionality — second to that, paying close attention to what very new users recount of their first experiences, because they might provide a glimpse into where it is failing for the silent quitters.
(Tool, community: same)