The key seems to be the same with these as everywhere else: you have to recruit and hold onto smart people, and be able to tell actually smart ones from people

The key seems to be the same with these as everywhere else: you have to recruit and hold onto smart people, and be able to tell actually smart ones from people who love to talk. In the setting described here, joining such clubs conferred considerable status and status was a desirable commodity. That made both attracting and retaining people who by and large had a lot to do much easier. On the other hand, it sounds like they struggled to keep the talkers from talking. Today I think the situation is reversed. You have essentially no way to generate anything valuable for your members outside of the direct value they get from the club, which is necessarily inversely proportional to their contribution to it. And because specialist knowledge is so much more valuable now, your focus probably has to be on keeping the people who don't want to talk talking rather than shutting up those who would talk to an empty room. The closest I can name to something like this is toastmasters, which has an aspect of self-improvement that seems to keep it going, or the Rotary Club which provides business connections. Neither (AFAIK) is in a growth period.