I first joined Reddit in 2007 when it was a genuinely friendly and informative place. The first big change came with the Digg exodus which brought mainstream meme culture. I think at that point, Conde Nast starting putting serious pressure onto management for Reddit to become more of a social network. This then led to the broken UI changes which, as you say, brought the wider bell-curve of humanity with it.
The problem is that Reddit simply didn't have the security controls/moderation in place for that type of activity. By 2016, Reddit was being widely manipulated by outside sources -- Large corporations were hiring troll-farms to shill their products; Nation-state actors were doing the same; political activists were trolling/abusing Reddit's systems in any way they could -- doxxing, death threats, extreme trolling...
And the friendliness and trust were gone forever. And instead of having discussions, it's now just everyone shouting over each other.
Now the management just want to cash out and using Reddit is now like writing a college essay while sitting in a McDonalds basmement eating a stale three-hour old Big Mac.
You're absolutely right. It's become a huge problem and not one that I think Reddit can easily solve given their infrastructure.
I've always had a fondness for Reddit, but I think its time is really over...