Discourage/ban Open threads. They are an unusual thing to have on a an open forum. They might have made sense when posting volume was higher, but right now they further obfuscate valuable content.

I'd say the opposite: the open threads are the part that's working. So I'd rather remove main/discussion and make everything into open thread, i.e. move to something more like a traditional forum model. I don't know whether that's functionally the same thing.