HN isn't just for totally new things. Lots of people wouldn't be aware of the existing stuff you mention.
So what if you and a bunch of other people have been long familiar with similar stuff? When you say it "isn't that interesting" you're just saying that it isn't that interesting for _you_.
So what if you and a bunch of other people have been long familiar with similar stuff? When you say it "isn't that interesting" you're just saying that it isn't that interesting for _you_.
[EDIT: "When you say" -> "When you say it"]