Locally, nearly all the radio clubs in this area have almost no membership outreach. They spend very little time or effort on "growing" the membership base.
One of the main reasons is that the club meetings and events are BORING.
For young hams, there is very little interest in regular club activities, it's just too dry and boring.
Why is this happening?
I blame the "Old Guard", the old farts in control of the club. These geezers maintain control over club activities, and direct them. They like "Old School", boring old stuff.
They meet once a week, or month, and eat dinner, discuss the club budget, and then things get really boring. I've been there, seen an heard it, and never went back.
If you want young hams to join, and stay in the club, you must stimulate the mind.
The club should plan events. Not just field day, or a seasonal hamfest. The club must plan and execute club events in the public. Set up a ham station in the public park, put up signs inviting the public to come, ask questions, have a snack, get info in ham exam sessions.
My local club stopped holding exam sessions over ten years ago. I think the VE team just got lazy. I feel there should be sessions held 4 times a years, come one, come all. It's better than nothing. I digress.
A public, active presence in the community, interesting lectures and demos, youth outreach and training young hams, these are what is needed to have a viable club with involved and active membership.
My Canadian ham friend describes his club meetings to me. They have all age groups, all classes of licenses, nearly full meeting sessions each week. They have demos and lectures on interesting subjects by expert members. They train all members to use the club station, which allows members that don't have their own gear to get on the air. They do public demos of ham radio, and try to answer questions asked by the public.
So, if you want a ham club that is growing and interesting to new members, the old geezers must give up the "stick in the mud" control, and get busy growing, or get busy dying...