Most subreddits would be better as things like HN in my opinion, a lot of the negative things to do with Reddit are down the way the platform is run rather than the format itself. A decentralised network where each subreddit is hosted independently and controlled wholly by its volunteer moderators rather than the (grossly incompetent in my opinion) side-wide administrators would solve many of the issues the Reddit format faces in my opinion.

But then you lose the network effect. reddit is so valuable because it brings together so many people from so many walks of life that would have never interacted otherwise.

Yes, I feel they've done that bit, AskHistorians is a brand in it's own right now. Seems like contributors could form a coop, have a subscription model, use it to fund research, etc..