"Misogyny and racism are why the public doesn't care about marginalized characters" No, the real reason is because so many people write these characters as marginalized before they write them as characters. They put the character's demographics first and foremost and neglect literally everything else.
I haven't read your stuff to be fair. If you don't do this then I don't mean you. But if you spend all your time on your characters talking about how oppressed they are and how angry they are about history and only ever show them lecturing people about sociopolitical issues and going to protests and stuff, that's not really a compelling character that audiences can feel attached to, even if they agree with the character's/writer's beliefs. Like I think the idea of nonbinary Transformers characters is great, I'd love to see some. But not written like Nightshade was, the writers didn't really give them any personality. (They did look really cool after they got their cog though, but I think they should've been a stealth bomber instead of an owl. Their body shape just feels more aligned with that alt mode.) I think the idea of lesbian, punk/goth and not conventionally attractive protagonists, especially if they're all three, is fantastic and I'd love to see more stuff about that. But that doesn't mean I think I Am Not Starfire is a good book and that Mandy is a likeable character.
In my opinion you should write your marginalized characters as characters who happen to be marginalized. There's too many people who put the cart before the horse and start trying to write everything around their demographics and personal struggles or about things they got bullied for in school. Come up with some good traits that don't have anything to do with activism and then shape their marginalized status around that core personality. Plus if you think about their traits first you can write about them reacting to injustices in different, unique ways instead of the one size fits all approach I usually see people doing when writing minorities.
TLDR, don't expect a character whose main defining personality trait is "they're trans" or "they're black" or "they're nonbinary", etc. to resonate as much with audiences as a character with a variety of traits, strengths, weaknesses, habits, hobbies, etc. That doesn't mean audiences are sexist, transphobic, racist, or whatever, it just means people want variety and to know how this character moves through a story and faces an assortment of different situations.