You're spot on with accountability. Why not just legally allow people harmed by following the advice to be ableto sue the influencers and allow those with proper credentials to become certified in the topic and certification protects from lawsuits?
Or maybe not the second part. Anybody giving bad advice should be sued.
"This isn't medical advice, but drinking battery acid will allow you to live forever." Would never hold up in court.
Freedom of speech seems to be the most misunderstood right.

Being Christian or going to church doesn't make you a good person any more than a speed limit sign prevents people from speeding.