There's a spectrum of decentralized <--> centralized for different audiences.

For this tech demographic here where installing some type of p2p or federated discussion tech (Mastodon? Matrix?) is not rocket science, it's more convenient for us to avoid that and just be on a "centralized" HN. I used to be very active on USENET and HN is relatively more centralized than a hypothetical "comp.programming.hackernews" newsgroup. This is not a complaint. It's an observation of our natural preferences and how it aggregates. (Btw, it's interesting that Paul Graham started this HN website but doesn't post here anymore. Instead, he's more active on Twitter. He's stated his reasons and it's very understandable why.)

For the phpBB forums where a lots of non-tech people discuss hobbies such as woodworking, guitar gear, etc., the decentralization perspective is the php forums and the centralization is towards big platforms such as reddit / Discord / Facebook Groups.

I see similar decentralized --> centralized trends in blogs. John Carmack abandoned his personal website and now posts on centralized Twitter.

My overall point is that a lot of us techies wish the general public would get enlightened about decentralization but that's unrealistic when we don't follow that ideal ourselves. We have valid reasons for that. But it does a create a cognitive dissonance and/or confusion as to why the world doesn't do what we think they should do.

EDIT add reply: >Wouldn't comp.programming.hackernews concentrate discussion under a single heading and also be hosted from a single specific computer?

Usenet is more decentralized/federated: https://en.wikipedia.org/wiki/Usenet#:~:text=Usenet%20is%20t...