Firstly, you have a bit of dissonance in your thinking that you’ll need to clear up. You say lots of complementary things about HN and suggest that the quality is what you’re aiming for. But you also say you “don’t believe in censorship”. Depending on what you mean by censorship (people have wildly different definitions!), you’ll need to reconcile the fact that HN has relatively restrictive community guidelines, and very active moderation. Many people would credit the high quality of discussion to those things.
Secondly, I think your “tags as subreddits” misses the point of subreddits. They’re not a filtering mechanism for which links you want to see, they’re a way to let users associate into small(er) communities where community norms, standards, shared experiences, running jokes, moderation expectations, and generally a community identity and spirit can develop.