Back in the days it would be "you can't just publish trial papers, it has to go through the church"
Technically, at our current World state, government regulations say that. And yeah, you have to have the correct credentials and submit your paper to the correct institutions.
Superficially, the system is architectured exactly like the one you are complaining, while in a deeper level every component works in a completely different way. What in practice means that it right now works quite well (could improve, but it works), but it's just a series of isolated institution failings (instead of a full system failure) away from becoming like the other. So, well, keep those institutions in check, but unless somebody comes up with a better system design, there's little point on complaining about it.
Today, we demand evidence to back up claims whether or not we want to believe them.
There were trials where it was shown that sufficient Vitamin D levels (most people are deficient) is very effective in preventing COVID. It got minor attention, but no-one is pursuing it on a widespread basis. Maybe it works maybe not, but even if there were clinical trials, it gets crowded out by what's being widely circulated in the media.
(That it often fails at this isn't a point in dispute. The fact that the medium entails a process and that the process, at least nominally, serves truth is.)
There's also the reputational role that such journals serve, effectively transferring the trust bestowed on the journal to the authors appearing within it, where trust is a belief extended beyond the extent of verifiable fact though not in opposition to them (as in the case of blind faith).
To that extent, and in a world in which each individual receiving a piece of information cannot independently assess and verify that information, your premise is in large part false: the medium used does serve to indicate the truth of a claim.
(As someone who's made a point of publishing pseudonymousely and in numerous online, unreviewed media, I'm aware of the challenges of trying to assert facts, even those which are reasonably independently verifiable, without the benefits of a persistent and highly-established identity or other indicia of trust, reputation, or credentialing. In balance I prefer the freedoms that come with this, though the challenges are also considerable.)
There are multiple occasions in history where a landmark paper was laughed at just to be proven right later. It hardly matter the medium you use to publish.
Social media companies take on immense legal liability when they allow high-profile figures to promote unproven medical treatments. The current approach obviously loses a lot of nuance, but the alternative is opening themselves up to litigation when, for example, users ingest fish tank cleaner after hearing from the President that there's a miracle drug which goes by the same name [1].
But they also laughed at Bozo the clown.
edit: I am going to add some sources, since I am not certain why the downvoting is taking place on this particular comment. Not sure how the statement is controversial.
[Biden himself admits issues with drugs]https://www.businessinsider.com/hunter-biden-opens-about-add... [Same thing only in his book]https://people.com/politics/hunter-biden-to-release-memoir-d...
If the issue had gotten full press coverage if might have flipped some states.
It’s also a reminder that tech companies can now decide elections. Angry denial is easier then rational thought.