Greed took over California because of the gold rush. It made people thirsty for wealth and land. There, in the newly drawn border between Mexico and the US, a lawless war for control, fueled by the anger and xenophobia of the past war, is led by a group of immigrants who join forces to create the myth of the Latin Robin Hood: Joaquín Murrieta.
Today we would use words like "Serial Killer" and psychopath to describe him, and that's fine. You walk into understand that the story is going to be told from his perspective and everyone is sort of the hero of their own story...
... only it's doesn't feel like it's told from his perspective, it feels like it's told from the perspective of (and very specifically) a white college educated liberal trying to be politically correct... and not an infamous Mexican bandit.
You can specifically see this from the dialogue of the white characters, which is even less realistic than the dialogue of white characters in a Spike Lee flick.
And then... it opens with and continues with a rock sound track which is just cringe. Young Guns did it too, but that was sort of Hollywood Bratpack tongue-in-cheek and used a lot more sparingly. Here it just feels like it's cheapening the story.
If they didn't want to go full western overture, there was a lot of music they COULD have used instead, but it seems like the rock was chosen to to try to be inoffensive and politically correct. Almost like the logic was western music tropes might be offensive, Mexican music might be offensive... let's go with bland rock... and it doesn't work.
And then, it really does lack even a remotely western feel.
It feels like it's made by people who don't know the historical figure, who don't know westerns, and are too busy trying to be inoffensive than make a good flick... and in the process they come across as incredibly offensive and inept.