Most of the people here despise sorting algorithms, and are fine with doing their own filtering, but to appeal to a wider audience, there should indeed be a way to suggest new joiners that they subscribe to a set of general communities that can be appealing to almost anyone. Of course experienced users can disable that, but that would definitely help.
By coincidence, I had to come up with a list of "active communities that are not memes, tech, news or politics", and here it is. It might be a starting point