I don't know... I think yes... and no....
I think... if an aspiring writers watches it and follows these video as a guide-line to dos and don't... Yes it is harmful.
But having that harm done and learn from is actually very good.
I don't know if you lot would agree, but writers tend to be fairly opinionated and we all have a our own ideas and the will to express them, right?
We discuss but we don't always agree. Which i think is fine (though you may disagree on that,
)
Disagreeing solidifies and sharpens out own ideas, when we try to justify our reasons. I help with how we think of ourselves, our style and our writing.
Someone who watches these vids and say "yea, I agree or no I don't know agree." follow by why? why do i agree and why don't I agree, lends to a deeper understanding of the writer's craft.
I remember reading Robert Mckee's book,
Story..... The perspective from
way back when all the way up to the 2000s, screenwriters took that book like it was sacred text. (it's not). But is was a starting point.
There were things in the book i disagreed with but i did not know why. Only after many more books, listening to many more varied opinions, and writing myself. I understood better and made up my own mind.
So in short, yes. It is harmful, but these videos are not the only place where other people will tell a writer what is 'good'. They are more "official-like" but in essence they are no different from fan tell writers what to write.
And if a writer can't survive that and still come out with their own agency.. then... *shrug*