You lost me at 'heroes are a/the psychological cornerstone of the storytelling experience'.
While I can agree that heroism is indeed one of the core character traits that goes into many characters across many genres, the existence of a significant number of fictions not including heroes not as a deliberate choice but simply because they don't need to disproves that claim as well as the claim of the video title.
I'd hear an argument that learning to write heroism is important for learning to write great stories in general, your working definition of heroism, while likely one of the only ones broad enough to belong in proper discussion of storytelling as a whole, is functionally meaningless on a case by case basis.
That last point isn't a criticism, it's a fundamental reality of subjectivity that you can't get over especially when the thesis of the video is already disproven by basic observation.
I like what you want to get across, but you need 30 more minutes of time spent talking to do it and someone arguing for the opposite side and the neutral stance at least in order for it to work I think.