I may be younger than you (I assume, based on various stuff of yours I’ve read), but I sure have felt the global impact of the 2008 depression, and I’ve been using Internet since 2006.
As I said, mailing-lists feel like IRC, meaning it’s an old-school types of communication over the Internet which for sure will never fully-die (and sometimes may be savors), but the actual usability in ecosystems like OSM may not be sufficient enough per group in order to keep them as active.
Yes, I know this reply is mainly for the topic of retiring inactive mailing-lists, while the current one is just about changing the clarification in wiki about pretty much how important it actually is to post proposals/votings in the mailing-lists additionally to the other communication channels. And it also depends to how many of the people who care about proposals/votings, use the mailing-lists as a sole or main communication channel.