The trend is definitely not there. The trend is away from IRC towards Slack, away from open web to walled gardens (or trashpiles) of Facebook, away from Usenet towards unfederated forums like this one.
>[...] away from Usenet towards unfederated forums like this one.
We're actually one step beyond that already, the era of forums is behind us, now people open a Facebook page or Subreddit when they want to create a community around a given topic instead of powering up a new PHPBB instance like they might have 15 years ago. Forums like HN are getting increasingly niche.
I don't like this trend but I think it makes complete sense. Centralized solutions offer generally better user experience (you don't have to monitor 10 different websites or watch your emails for notifications, you don't have to create dozen of accounts etc...), they're easier to develop, easier to maintain and, perhaps critically, easier to monetize.
These days I only see the cryptocurrency communities betting on a decentralized future (instead of merely wishing for it without much hope like I do).
