Why "Supergirl" Failed.

The new film "Supergirl" has not performed well at the box office.  

Pictured: the public's response to "Supergirl".

The on-line punditry on exactly why this is so is nearly limitless.  It's Superhero Fatigue. It's Fear of Female-Leads.  It's James Gunn.  It's the budget being too large.  It's mistaking a secondary character for a primary one.  It was "Creative Differences". It was studio interference.  It was the writing (or the editing or the filming or the action or the lack of action or the muddiness of the action).  It was too feminist. It wasn't feminist enough.  It used feminism as a ploy.  Literally the only aspect I have NOT heard blamed for the film's failure was Alcock (the actor playing Supergirl), who seems to have acquitted herself well.

I don't want to dismiss any of these possible factors; but, in fact, I don't want to talk about them at all. Instead I want to point out the one problem that seems obvious to me. The one that let me know from the very beginning of the project that it would fail.  And that the reason it was obvious to me wasn't some special insight on my part.  I just happened to be... a comic book reader.  And that reason is:

it's based on Tom King's Supergirl: Woman of Tomorrow. 

I have seen this miniseries described in the comic book press as a "fan favorite", and the only time the comic book press uses that description is for something that is exactly NOT a "fan favorite", but rather "something only diehard fans even know about". In it, Tom King has Kara (Supergirl) drunk at her bar at a birthday, which is already, you know, merely a modern "counter-intuitively edgy" interpretation of the characters that fits poorly.  Then she goes on a Hero's Journey, blah blah blah, but the damage to the character is already done.

This approach is at the heart of Gunn's version of Supergirl (even though no one likes Edgy Supergirl, no matter how many times writers time to go that route as a cheap way of distinguishing her from her famous cousin).  No one liked her that in the Superman film and, unsurprisingly, no one wanted to see a whole film based on that.  

And trust me; as I have made clear before, I am not someone who believes that Supergirl needs to boundlessly optimistic. 

That fact alone was going to doom the film, regardless of any other factors.  I knew this; so did most Super-fans.  

Or even anyone who watched more than one episode of the Supergirl show.

How come this is one the decision that was never questioned (or is credited for the film's failure)?