I keep a forum going that's been up since 2007 for hobbyists. I keep it going because of the priceless historical information on it, not the present quality of discussion.
My sense is that people have become less literate, less polite, and less patient.
Again, this is for a simple hobby so there aren't necessarily many intellectuals in this hobby, but 10+ years ago we had many lively, intelligent, long discussions.
What happens is you start getting more and more users who barge in, hijack threads, and do not contribute anything useful.
They can also be abrasive, which spooks the old timers from prior generations who were used to intelligent, polite discussion where they agree to disagree.
Eventually the quality content thins out, and there's a sort of Reddit effect where you get one solid reply for every ten useless ones.
These days I find most of the new users are just looking to find out what their collection is worth.
As those new users fill up screen space with vacuous content, the old timers are fading away either through attrition or illness or death.
On the technical side, you're constantly battling bots because your domain age and reputation is targeted by spammers.
