I honestly agree with you in many respects, I'm simply spinning in some nuance to a topic I keep seeing.

The snake oil salesmen is productive precisely because the actual effects of the snake oil they are selling is unknown to the consumer they are introducing it to. There isn't easy answers to this, it's just a fact of life that we can try our best mitigate.

And apparently fish oil actually does help your brain. Weird world we live in.

So I think the focus on "experts" is actually a consequence of declining institutional credentialism. You didn't trust them for claiming to be experts, you trusted the institutions who called them experts and said you should trust them for that reason. But expertise implies competence not trust. Not everyone operates with good intentions even with the right credentials, including many institutions themselves.