Maybe 5%.
We are about 50 members, and the inflow of new members is not bad.
Now, if we had trash bins from Schweizer on display, we'd been long gone.
I've soloed and lateron instructed in Ka7's (which could be considered as the "European 2-33", just being 30 years ahead), but that was 30+ years ago. Who wants to dwelve on the middle ages?!

Certainly a Ka7 or your local variety teaches you how to fly, but so does any modern glider.

You can't have 2-33 in a club AND complain about dwindling membership. And yes - even in Europe we had these things, but must club managements managed to build up the switch over time. And tell those folks who claim that dinosaur gliders are the best way to learn the real thing... to go to hell.