The textiness of the site likely scares off a lot of new/non-techy users. Reddit switched from being a text site to a modern UI a few years ago, in doing so they managed to gain a lot of new users. Which in turn ruins the sites community and discussion when users are focused on making cheap jokes and memes for upvotes.
I think I agree with your main point but some distinctions are important. We don't want to scare off new users—we love new users. We don't want to scare off "non-techy" users—they are completely welcome. The users we want, though, are the intellectually curious ones. And there I agree that HN's textual orientation is an asset.
