The greatest success of capitalism has been dividing people along gender and race lines - not letting them show any class solidarity. If people did, they'd realize that the difference between a poor white and a poor black is a rounding error compared to the difference between a poor guy and a rich guy.
Speaking of "dividing people along gender and race lines".
It is fair to ask why in recent years movements and media have focused more on race- and gender- based solidarities over class-based solidarity, compared to a century ago. And a strong argument can be made that Capital is the primary nexus of power in the world, and in the end it really doesn't care that much about safeguarding patriarchy or white supremacy. Hell, breaking down those barriers often just generates new grit to be thrown to the mill, so it's commonly profitable to break them down. It's much lower hanging fruit (though still fruit that's worthy of harvesting), so people focus on them more.
Along the same lines, our educational and media systems have given us the imagination to envision a world where racism and sexism don't exist. Not that they're easily achievable, but it seems almost natural that a century or two from now they'll be gone. But social and economic class? They seem as immobile as Mt Everest.
ETA: Also, I think you're doing a disservice by writing off black activists and feminists. Obviously every person has limited perspectives, but you're just trying to pick a fight that doesn't need to be picked. Never pre-emptively write off a potential ally.
The difference between a poor white guy and a poor black guy is that the poor black guy lives in a system where they've suffered generations of sustained oppression and subjugation.
I'm baffled at how you made this a race issue.