This website is good about it, mostly because it has a very strict no politics board. I think the only time it was a mess was in the COVID threads, which rightfully got shut down after how much of a mess they were.
I think it's overly simple to say "this all boils down to the 2016 election", because there was a lot of shit brewing that went under the radar before then, but you'd be insane to argue against it being a major factor. That election emboldened both shitty people who loved Trump and shitty people who hated Trump to become more radical and more polarized, and social media is the obvious outlet for that because there are no consequences for it. Especially if you hide behind a fake account.
Now 8 years later, people are just openly shitty on these social media platforms because they've done it for 8 years with pretty much no consequences. No matter where you sit politically, you can find somewhere to be a piece of shit online and face no consequences for it.