The pink elephant there is profit. Discussion with strangers is not difficult to solve. Even going back to AOL style topic driven chat rooms, which are just a step above IRC, it all worked just fine. BBS style systems also worked phenomenally well.
But now enter companies wanting to make a buck. And that's where all the stupidity comes into play. Because now you need to people to disproportionately be exposed to e.g. advertisers, and to keep the advertisers around you also probably need to stop people from really speaking their mind about them: 'This movie sucks.' 'Yeah, drink this fizzy corn fructose laden crap and get fat. Woot!' So you end up with shilling, 'moderation', and other mechanisms to try to help ease monetization. This, in turn, rapidly drives division, antagonism, and trolling. And so the corporate site needs to push even harder to maintain their advertising venue. Which results in an ever downward spiral.
And on top of all of this now you don't just need people to chat. You need for them to stay actively 'engaged' with your 'platform.' Those big buck advertisers aren't going to pay you to advertise to your 500 users. So now enter things like voting systems. Opaque manipulation means you can help drive discussion however you want, and you can simultaneously help addict users by giving them that tiny little dopamine bump each time they see 'oh wow, i got more imaginary internet points! herpa derp!' Hey what do you know, these voting systems are somehow driving the creation of increasingly radicalized little echo chambers. Yeah man, but look how engaged they are! It's all quite idiotic, but this derives from the fact that the problem is not enabling chat, the problem is enabling chat while making money off of it.