I've been here before. A site I co-founded  (I wrote the code) to replace a forum shut down by Microsoft (we launched exactly one year before 9/11), with thousands of users and thousands of posts per day for several years. Overall quality not as high as ET in its heyday, but a lot of wonderful things, and high quality human interactions.
The decline commenced with the second Gulf war, a clear left/right split, and the right founded their own site and left a couple of years later. The site was still viable until its 10th birthday, but after, it limped on as a club for old members for a few years (good for poetry and literature), then died.
Last year one of the participants asked me if I could put it back up, so that she could recover her writings from fifteen years ago, for her Ph.D in education. We managed to do that.

For me, social media killed the whole notion of a specialised forum site. Personally I have never been able to separate the personal from the political, and in fact I still feel that it is fundamentally unsound to do so. I was a latecomer to ET, but I enjoyed the crossover in that respect. I tried sporadically to follow the migration of the personal side to Facebook, but that platform has always filled me with horror and dread, and I have long since abandoned it definitively. Which leaves me as something of an orphan, currently.

But I'll get over it, I suppose.

_{It is rightly acknowledged that people of faith have no monopoly of virtue - Queen Elizabeth II}