Commenting under most articles and blog posts is useful to the author as well as the audience. It allows for corrections, additions, and other feedback. Utility of comments however dramatically diminishes under popular articles in media and on social networks that attract dozens or hundreds of comments.
What happens is that the comment section is quickly flooded with low quality comments that nobody wants to read. Popular articles are perceived as a stage. They attract people who just want their opinion to be heard without having something of value to contribute. Moderation can remove obvious spam and trolling, but it does nothing to improve overall comment quality.
Worse yet, all comment sections give advantage to people who post first. They get the most visible position if the comments are sorted by time of posting. Sites are trying to counter this with voting, but by the time someone posts a thoughtful comment, the quick comments have already accrued a lot of votes, which causes any late responses to be buried at the bottom where few people look.
Sites can try to give new comments an advantage by holding them at the top for a while, so that they have a chance to collect upvotes, but quick comments still win, because the longer exposure gives them more opportunities to accrue votes. This inherent advantage given to quick comments combined with people trying to use the article as a stage encourages people to post poorly thought out comments, often without even reading the article.
Arguments between commenters create lengthy subthreads with little value to the reader. Some sites try to counter this by folding subthreads, but that just encourages people to post more top-level comments with little added value.
The idea of large comment sections is that they aggregate different viewpoints. But what really happens is that people holding mainstream (usually naive) views will completely swamp the discussion and upvote each other. Voting encourages groupthink. The way to be liked is to say what everyone else wants to hear.
The overall effect is then that the top of the comment section ends up consisting entirely of slight variations of the same opinion. Meanwhile original (sometimes expert-written) viewpoints are buried at the bottom, collecting downvotes from everyone who passes by. There's no technical solution to this problem, barring major advancement in AI that could deduplicate the comments.
Publishers could severely restrict comments, perhaps even down to the level of a curated list of related articles, but they have little incentive to do so. Comment sections serve as low-effort content farms that bring in traffic and engagement. And article authors, if given strong moderation mandate, are unlikely to pin or link to responses they don't agree with.
Ultimately, the burden of responsibility is on the reader, who has to refrain from posting to any heated discussion. The general rule is that if the discussion is too long or too low-quality to be worth reading, then don't read it and don't post into it. Comment sections are useful only to gauge majority opinion among article's audience. Any non-mainstream or expert opinion is better placed in a standalone article, which offers time and space for a well-written multi-faceted argument.