I think what you're saying here is not that politics are terrible on microblogging platforms, but that microblogging platforms are terrible, which is a pretty valid sentiment.
His reasoning was complex but a lot of it revolved around the simple fact that as you get more people publishing, the intellectual quality of the average published work goes down.
I'm not ready to roll back the printing press, but in retrospect the digital era has proven him right about this. For instance his position kind of predicts Eternal September - the easier it gets to post online, the more numbskulls you have doing it. Microblogging is the ultimate expression of this and frequently the content you find on microblogging platforms is the absolute worst hot takes and generally the most vile stuff the moderation rules will permit because shock value generates impressions. It's every idiot on earth competing to be as flagrant and base as possible.
We usually hold up free speech as a virtue in Western societies and there are a lot of good reasons for that, but I'm increasingly inclined to treat microblogging less like publishing, and more like alcohol/tobacco/gambling, like it's something people do but they know it's not good for them, they do it anyway because it's addictive and easy.
He argues for a society where people are both free and equal, but he recognized that some forms of inequality could coexist with freedom, provided they were rooted in merit or necessity, rather than arbitrary privilege. Also, when he talked about the Rights of Man, it wasn’t a rhetorical flourishes, he did mean man.
It’s a mischaracterization too to say he hated the democratization of publishing. His own ideas gained traction precisely because publishing allowed them to reach broader audiences. His critiques of printing and arts weren’t aimed at access itself but at the unintended consequences that came with it.
From the viewpoint of a library patron, for instance, feminism is a literary movement because it has left behind a large literature frozen in amber.
The earliest authors of the second wave, say Friedan, Steinem, or de Beauvoir were good reads but in 10 years the movement becomes a lot more “vulgar” (in the Latin sense of “common”) and at its worst you find large format books, cheaply bound and typeset with illustrations that probably got mimeographed before they saw the lithography camera full of radical and sometimes hateful rants.
Traditional online communities -- BBSes, IRC channels, Usenet groups, even standard blogs -- are all self-contained spaces that have their own norms and expectations, and so preserve the ability to have communities with high standards and high-quality discourse amidst others that fall victim to the kind of regression to the mean you're talking about. HN is a great example of this (as compared to other sites), as is Reddit, where the differences between various subreddits are very apparent.
But social media lumps everything together into a single space, where each participant is looking at a slightly different subset of the whole, and this causes the rot to overwhelm everything pretty rapidly.