Both of them are great platforms but we need alternatives (for the sheer reason of increased competition, if not anything else).

I'm not a huge fan of "design heavy" platforms like quora, twitter and FB, I mostly prefer "content heavy" platforms like reddit and HN but unfortunately it doesn't seem like more people prefer them. There are hardly any active ones on any platforms apart from these two. I know about hubski and raddle but they are mostly empty these days (at least for my tags/interests). Do you know of any other good ones?