> 4chan is usually demonstrably and objectively worse than any mainstream news at sharing important, relevant, and true information.
Are you talking about trivial news reporting ("this thing happened today")? If so, yes.
If you're talking about important questions in society, no. I mean, if you want full-on propaganda you can read the New York Times or The Atlantic, or Washington Post, etc. Aside from tangible reporting, your probability of finding truth about important questions in society is extremely low, while they tout it to be really high -- extremely disingenuous. And yes, in all of these places the Opinion section has adquired so much relevance that they are no longer newspapers in the traditional sense.
On the other hand, if you want actual truth, you'll have to read through tons of bullshit, slurs, memes, jokes, fake news, fake tweets, CIA narratives, Mossad/JIDF narratives, but it will be there... buried somewhere deep in a 4chan thread. The great thing about this is that there's no pretense, it's: come at your own risk, use common sense, take everything with a grain of salt, "everything said here is satire".
> Note specifically that in unmoderated channels, governments already do participate with propaganda
That's definitely true, there's even specific slurs for those pushing propaganda. But that's the beauty of it, there could be conflicting narratives being pushed at once, and there's no way to tell whether someone believes it or is just shilling. At the end of the day, it's just an anonymous comment and you can only determine it's value based on the content of the post. You can't even safely tell if it's a human or a bot nowadays.
I have no doubt in my mind that the free flow of information is always better. Now, you can argue about the practicity of this, and you'd be right. The thing is, this is a symptom of the state of affairs. Think about it, there are 8 billion people walking on Earth, a great proportion of which have a computer with an internet connection and a high quality camera in their pockets. That means that this year will be the most commented on, most recorded in human history by far. On top of that, there are governments around the world spending billions of US dollars in propaganda. It's no wonder 'truth' is obfuscated and almost impossible to come by.