Hm, it is very doubtful that good content is simply enough nowadays. With tons of information in the internet, "just good content" can hardly be discovered by itself. There are should be ways for target audiences to find it, share it and engage with it.

That is not garbage, that is exactly what he's saying: do something interesting, then share it with the people who are interested in that kind of thing.

It's the eternal debate: is content truly king? Can you just push awesome content out there, and get floods of traffic in?

Or is it a "If a tree falls in a forest..." type situation in that an unknown website with great content will continue to be an unknown website?

Since Google can't truly understand content quality/semantics, a certain level of marketing does seem to be needed to bring traffic in.

You'll need to attract attention to it in some way. HN, when done right, can be a way to do that.