So any article under the sun is relevant for HN? That's definitely not the case as mods frequently remove posts, and as much as they would like to be, mods are not arbiters of intellectual curiosity.
I find it useful to look at the submissions by the site's creator[1], before he passed over the site's management to others, back in 2014. As you'll see, it actually has very little engineering content, and on the contrary, has many articles from mainstream sources.
I'm sure HN has ebbs and flows on the ratio of engineering articles, but it was never supposed to be dedicated to those; maybe you just joined at a moment when the ratio was bigger.