The Internet is a vast resource, but no one forum or platform satisfies my particular interests, which are always morphing. In some ways, you have to create your own network of contacts, friends and resources. I've found that most audiophiles, designers, manufacturers and engineers are pretty generous in sharing their knowledge. You'd be surprised at their willingness to talk with you if you email or phone them.
I took a look at some of the discussions you started and many seem to be about DIY tweaks--DIY Audio is yet another resource you might tap into.
I developed relationships over the years, some from contact on chat fora, that have endured. This, despite the fact that some no longer post at Audiogon, perhaps for the same reason you identified. I guess it is incumbent on you to seek out the knowledge you want and find the people who can best fulfill your needs. To me, there is no "one stop" place for that. And part of the enjoyment, for me, is the research and learning, which has its own rewards.
Good hunting.
Bill Hart