To most, consensus and truth are the same

Argumentum ad populum, the fallacy that if most people agree, they must be correct.
We're tribal animals. Going against the group is usually a bad survival tactic - but just because you echo the beliefs of those around you doesn't mean they're right. Very few of history's great philosophers held popular beliefs, yet we still remember their names. Nobody remembers the conformists.
- The opposite is also dangerous, i.e. believing reflexively in heterodoxies and conspiracy theories. But your point stands.
  
  If every youtuber promotes something, its likely something bad.
  Not always.
  But very likely.
  ahem Honey ahem

"Millions of flies can't be wrong!"
- The flies aren't wrong. Eating shit is good FOR THEM but it would not be good for humans
  
  Speak for yourself
  
  That raises the question of if you're another fly or another human.

In theory there's no difference between theory and practice, but in practice there is.

So say we all!

Consensus is the instinctive collective response of the mind to the world whereas truth is its regimented output. This is most obvious in the evolution of language, the truth in this instance is things like definitions, syntax and grammar but this is all after the event and looking back explanation. The real growth of language is from consensus. The definition of the word gay in original form by etymology was carefree and happy which is it's truth but by consensus of usage it was altered to mean homosexuality, which is an entirely separate definition. The consensus idea very easily overran that of truth and became what is real.

So say we all.
SO SAY WE ALL!

I mean, that's just common sense

Yeah, you are right. Too many people in the sciences believe this as well. Science is about repeatability and falsifiable hypothesis...
- Isn’t it the case that “consensus” in the sciences is just a shorthand for “we agree that this is most likely to be true”?
  If I were conversing with a scientist and I asked about possibility x, and they disagreed with it for the reason that “the consensus is…”, I would assume that they are not saying possibility x is wrong, but rather that they would need really good evidence to agree that x is correct.
- I don't remember the exact quote, but I love the thing about "the thing about science is that it doesn't matter whether you believe it or not."
- Yes but it's worth pointing out that peer review is also a form of consensus-building. It's not a perfect process, but it's pretty workable if everyone's pulling in the same direction.
  
  Peer review is a sanity check, but many incorrect theories disproven later passed peer review. I only point out science as a the one group of people who should be above appeals to authority or consensus but they are still very influenced by it.
- Expert consensus has a different role than the OP. It’s a statement made by people who are intimately familiar with a body of evidence and are consolidating the many narratives of that evidence into clear statements.
  Yes, it’s not true merely because they say it’s true. It’s most likely true because these experts have analyzed the thousand tiny individual pieces of evidence out there and have determined they are all pointing to the same key conclusions. That’s not an argumentum ad populum, that’s analysis and interpretation. Ignoring that because you saw some TikTok video is the actual fallacy (argument from authority.)