Some time ago I took a voluntary time-out from the forum. It was already flagging at that time. I think that nowadays it has reached a state where there is a core membership who all more or less know one another's views on most topics, perhaps it's like a long marriage where the initial excitement has worn off.
There are a number of issues with sites associated with unusual phenomena. One is they instantly polarise opinions, another is they eventually exhaust peoples' contributions as you say, and there's also the thing where every phenomenon is treated equally so long as it's off-beat.
A case of the latter is the Fortean Times. It started out as a post-hippie mag run by a sci-fi fan and a former situationist and offered clippings and articles about weird stuff in a largely unmediated way, except for the occasional wry comment. At no point did the editors claim the reports were true or untrue, but included them as being within the bounds of possibility. Fort said he was not interested in singularities, but repeated phenomena, and content fell into a range of themes. I first came across it in the 70s and took it regularly from the 1980s. It was definitive lavatory reading, thoughtful and good fun. The original editors wanted to retire around the millennium and it was sold on to a bigger publisher, who in turn passed it to someone else.
The FT forum today is a parody of the original magazine. Moderators are openly materialistic and partial and subjects are largely treated as "true" (science based posts) or a comment on the unreliability of the human observer (everything else). Contributors are banned if they
don't get it and the limits of discourse are uncompromisingly imposed. When I last looked, some time ago, it was sock puppet hell and mods indulged the status quo. It really is sad to see what happened to the old mag and I stopped taking it years ago. The treatment of all phenomena as worthy of note is a noble enterprise, but the old FT was largely free of debunking whereas the forum is a skeptics playground.
How you keep a site vital for proponents and dissenting opinion engaged, I don't know.