Do you think your considering HN a clear exception to being “Reddit with a sense of grandeur” might have more to do with your vantage point than your ability to gauge the value of online communities?
Yes, honestly i think this is the largest contribution to HNs successful place in its niche. Every other website turned from articles to images to infinite scroll politics and gifs. They all did that because it sells more ads. HN has never made a design change that prioritizes anything over articles. And even when it does conform to the greater trends of most people reading comments over articles (increasing bubblifiation of popular beliefs) the comments are much huge quality here because we're all the kind of people who like a site with articles, and thus more people actually read the articles, and the feedback does not include the internet ubiquitous "social credit score" seen on numerical stats around every comment on nearly every other website.
I mean that referring to "HN for X" is like (more than a decade ago) "Facebook for X".
I consider HN a clean exception to most (all?) online communities in which I have been participaing; in all other cases, the quality tanked, they became ghost towns, or they just changed from their original goal.
Sure, there are many wonderful forums and special interest groups, and it is good that new ones have been created. Just HN is not something you start at, it is something you become.
It has everything to do with the simple fact that HN was launched in '07, when Reddit wasn't that mainstream.