I'm all for keeping RS a private forum till it dies.
We're all still here because this is the format we are comfortable with and like. I'm positive that switching to a different channel of communication (discord, fb group, reddit sub) would basically be the end of RS as we know it. There may be new people that join and the name is kept alive, but it wouldn't be the same anymore. All the other forums i've been in over the decades that switched to FB group have just become people posting pictures and selling stuff. there are basically no real discussions, just very surface level comments (and bots/trolls) for the post of the day and that's it. Let the kids have their thing, this is what we got
Having said that, there's nothing to stop people from creating their own discord channels and reddit subs if they feel it's viable (while we keep the forum). but i dont think a lot of users would migrate.