In regards to this shitshow
I believe that Tumblr users, and especially Tumblr Marxists, have got to let go of the idea that every issue (or even most issues) have one objectively correct answer, that they personally have it, and that anyone disagreeing is trying to be wrong or make them be wrong or harm people somehow, and that this post is a great example of that. The OP has a valid perspective; lots of mass-market fiction is written poorly. But she places the blame squarely on only one cause: people who start their creative processes by creating characters. Her insistence that this is The answer, and her unwillingness to consider that other perspectives (e.g. perhaps the commodification of culture under capitalism results in publishers choosing poorly-written but easily-accessible fiction to publish at an abnormal rate in order to boost sales figures and thus corporate share price?) may be equally valid to her own, results (it appears to me) as her taking any differing view as either someone who can't handle the truth or someone who is trying to attack her. She responds as if it were an attack, which prompts another response in kind. Now we have a shitshow.
And this isn't unique to her, and I don't know enough about her to say if this is a character flaw or just something she's doing right now, and I'm not saying I'm objectively correct here (that would be pretty hypocritical of me!). But it appears to me to be a logical explanation for what's going on, and something I think can be seen in a lot of historic arguments across this website. I think Marxism comes into it because a lot of principles of the various Marxist ideologies (like the democratic centralism model, strict hierarchy, and centralized planning) are based off of the ideology not just being correct, which any ideology believes to some degree and therefore isn't strange, but that Marxism itself is a science, not just an ideology. That raises the stakes—there can't be multiple valid perspectives on an issue under a Marxist ideology, because that's not a factual, definitive, scientific conclusion. And Marxism is a science, so it has to be always right and always definitive. Ignore the fact that different forms of Marxism have different "scientific" answers to the same question.
It's an unearned, mandatory self-assuredness that I've seen all over Tumblr, by people who believe all sorts of things. So it isn't limited to Marxism, of course, but I think that's a relevant piece of the context for this particular shitshow given the OP is part of the Tumblr Marxist wider circle. I think people on this website just don't put enough value in saying "hey, I could be wrong, but this is what I think", and accepting that disagreement isn't inherently an attack. We can say whatever we want on our own blogs, but if we engage in critique, others are likely to respond with their own critique as is their right just as much as we had the right to critique first. You don't have to take people being assholes to you, as many people are being to OP (though it's often useful to consider whether you set that abrasive tone in your opening post when deciding how hard to push back), but equally people being assholes doesn't then give you the right to claim that everyone disagreeing with you is stupid. Just... If everyone remembered they can be wrong, and put a little more value in de-escalation, even over things that don't matter to them personally, I think this whole place would be a lot more tolerable.