"It's somewhat astonishing that despite being open to non-RF stuff, this forum has not been completely taken over by the vast majority of non-RF users out there."
Exactly right, which is why the forum has stayed relevant. Things are fluid and flexible here, not fixed and rigid, and opinions are all over the place. I almost always shoot film, but it's amazing what quality you can get from a phone, and that's pretty neat. As new things develop, this forum is ready to go.
I doubt it was ever meant to be solely about rangefinders anyway because that isn't sustainable. It would be like having a forum for folders only, or TLR's. That leaves out a lot of people. Primarily rangefinders perhaps, but the different categories mean that almost everyone can find something of interest. The more diverse the better, and I think that a very diverse membership and sensible moderation has been the reason for its success and longevity.
We very, very seldom see posts that would be considered rude, or denigrate others. Go to Reddit sometime. I had to end my membership there because certain people were totally out of control, and even though many people complained, nothing ever changed. After a while you say this isn't fun anymore and you stop going.