From what I can make out from being a forum member for the best part of a year is that there genuinely is a lot of useful information already on this forum and I'm always searching for things I'm interested in and usually hit upon something useful/interesting to me.
I agree that there have been some "open" spats, and there appear to be some strong views about this company vs that company etc (especially servicing costs, tuning etc) but even those discussions are useful - we all have our own opinions.
I also think a large % forum members have had multiple GTR's (of different types) and therefore probably used the forum more when they first got their cars as owners were finding their way through sorting out servicing/tuning etc and what works, what doesn't, where to go etc etc. That learning curve is probably less now for all models, no real science to it, just the passage of time.
And that I think is one of the main reasons for the post count dropping - either you can find the answer to your query by doing a search, or if its something quirky and never happened before/reported on then ask away via the forum. And there probably isn't that much of the latter, so much has been covered and shared already on this forum (and others).
I believe this forum to be one of the best I have ever used, the members certainly seem to be welcoming and despite being asked tens of times a year about which brake pads to use, or what's the fitting sizes for the undertray bolts etc etc? most questions/comments receive a good reply.
I'm not a fan of FB and social media in general, for me this forum is great in what it offers (quiet or otherwise)