The Mennonites have the most "religious exceptions" to getting school vaccines. We're seeing the results of that. They likely are not seeking advice from anywhere.
I don't think "most people" get medical advice from social media, obviously a fair number do. We particularly see popular diet fads come and go.
I also think the country is still in decent shape overall despite obvious issues.
I do look up "medical advice" from sites I think are good, Mayo Clinic etc. The "seed oil" thing is bouncing around a lot these days.