Sure, free speech is optimal if this happens. But what if it doesn't happen? People are extremely irrational [0], and that certainly won't change anytime soon. What changed is that we got better at exploiting that irrationality at scale.
There's no practical value in stating "in an ideal world, free speech is the solution". We don't live in that world, and we don't get any closer to it by complaining on HN about people not doing enough critical thinking.
Fact checkers, corporations, the media, the state, and any of the elite are just people and so extremely irrational, Why on earth would you want to give any of them power above and beyond the general public, it's so easy to manipulate the so called "rational" with selective publication of information. Do we just forget that covid human to human spreading was "fake news" for an entire month, and basically changed the course of history because some bureaucracy decided it had more authority on the matter than a doctor treating the patients.
Or what about the "Ricard Spencer is a nice guy in Germany" effect, because people in Europe can't see the hate speech he makes, so they think he's fairly reasonable person.
To me it seems that it's the general public, from Snowden to Li Wenliang that is keeping fake news in check, not the elite, keeping the public in check.
I think a few broad trends reinforced each other in the U.S. But kind of prerequisite, people came to get too much of their notion of free speech as a scholastic doctrine in state schools. Mills's On Liberty argues that a doctrine elevated above criticism comes to be held in an empty way, and gets lost over time even if it's true. It seems like that happened here to the idea of free speech itself.
(I'd quibble at your "completely destroyed". We don't want to see what completely destroyed will look like.)
People need to adapt to not believing every stupid thing they read on the internet and actually thinking critically about things. The information streams of the world should not be tailored to the critical thinking ability of complete morons.
It blows my mind we went from "trying to censor cop killer is a bridge too far no matter the merits of doing so" to "you can't say things that compromise the interests of powerful individuals, offend the chronically sheltered, or that might confuse the braindead under any circumstances" just in my lifetime. Free speech seemed absolutely unassailable in my youth and has been completely destroyed relative to that in present day.
What the fuck happened?