I have a slightly different take. I think it's aimed at an audience that has to know nothing about the character to even be entertained.
James Gunn made James Gunn movie ten years too late.
Supergirl is my favorite comic book character. I had infinite hope and knew without a shadow of doubt that they'd crush that hope mercilessly.
They picked an 'award-winning' poorly-selling comic arc (no issue made it into the top 30, even just DC's top 30, and sales declined each issue). They picked a story that required you to care for Supergirl before giving an audience any reason. They took a character of intelligence, compassion, and hope and gave us an ad for SSRIs.
They picked an actress who, politics aside, also didn't look like Kara in any appreciable way.
The movie had serious plot issues (watch Pitch Meeting for Supergirl on YouTube if you want a humorous list).
They ignored what made Kara who she is, what set her apart from Kal, and turned her into a self-loathing, self-destructive, nihilistic low-grade moron.
There was a tug-of-war between Gunn and the director over many aspects (editing, music), and Gunn threw his studio position around to win it.
All of this is borne out in the fact that Supergirl 2026 set to lose double the amount the 1984 movie lost, adjusted for inflation.
They took Kara and squandered her and now I'm going to have to wait until we've colonized Mars and achieved world peace before I get a new version of her on a movie screen (if they even exist by then).
Bravo DC and Gunn. If only this failure of 'modern audiencing' were predictable beforehand.
Oh wait.