My first review so I will keep it shortish.
Documentary is interesting but it is too long (1h40min) for what it has to offer, it gets repetitive midway and becomes tedious.
It is not that documentary fails to bring depth of villains in DC universe so much as there is not much depth there. Sure we can talk about Joker, Luthor a lot but generally DC villains few general assets and what enriches them are their origin stories.
Problem with DC and Marvel is that there is no real progression of characters and annoying thing, what has been tried to be represented in documentary as 'shocking' episodes where Batman gets his back broken by Bane, Superman dies etc., is that our heroes and villains will always come back, get re-booted and we can read all over again.
While watching documentary that became more and more obvious, it is great ideas getting tediously recycled and invention of new story arcs made them look desperate.
So in essence documentary showed me that as fun as they are, commercial comics have become ... well repetitive and boring. On a positive side I have grown to respect even more Game of Thrones books / show series where characters are build and destroyed, story goes on and character progress.
There has been some shocking moments in comic book history, but what is the point? What is the point of Superman getting killed only to be revived, like nothing happened. No character progression just same old, it was fun when I was kid but not anymore.