I kind of feel that the difference between an AV forum and a computer forum is pretty vast...If you want a forum with more members staying for longer and discussing more tech topics look at: AVforums there is a large community there. Computers and computing is just a small part of their topics list.
On an AV forum you'll still have people discussing the merits of oxygen free copper vs silver etc. (And what about putting gold connectors in the setup?)
But with computers now... For most of the world AV is something that you want to do in your down time, and want it to be good, picture and sound quality matter... But computers, have become essentially just tools.
Not that people won't still drop a grand on a PC and want it to be the best, but you know it's not going to last as long as dropping a grand on a decent tv or hifi...
And most people don't want to disappear to another room, they like portables, less choice, little to no customisation... Nothing really to discuss, pick a machine and use it.
Also, much as it feels silly to say it, actually there just aren't the kind of computer problems there used to be, for the most part, since Windows 7, The OS has been pretty bullet proof, doesn't crash randomly, etc, same for software: developers up'd their game to the extent that people just don't need help getting regular stuff done. And if you want advice on the professional end, you just go to professional product forums. (An example of this is I needed advice last week on a multi tenant cloud backup solution that we run where I work. -how to extract specific stats...) it would have been a waste of time to ask on any generic forum.
They also have social media presences, links to share content on Facebook and Twitter, -something we just never got off the ground here. So there may be an argument that they are simply managed better...
That all said:
They have pretty much the same problems as we do here, just hidden three layers deep. Loads of the forums are last post, today but hours ago, or yesterday, a week ago etc...
The forum format is dying. It's a slow death, and I wish it weren't happening...
The UG forums, (being pushed by an international publishing house, with all the opt in social media guff) slowing down is a pretty good testament to that. (Though obviously you can't read too much into individual data points.)