I see what they’re going for and I think it’s good to have diverse perspectives represented, but if you actually said this to a “white cis guy is the default” person they would just tell you “this is America, not China, and white cis guy is the default here. Just look at who is rich and successful.” It’s not the gotcha the original poster thinks it is because it’s appealing to a greater view of the world than the racist, sexist person wants to have.

If someone told me the protagonist should be a white guy I wouldn’t directly tell them they’re wrong, I’d express my own counter opinion that I don’t want to see the same thing over and over again, I want to see new stuff, and seeing another white dude is boring and therefore kinda lame. Maybe point to accessible movies like how Annihilation has cool action and visuals but also a distinctly feminine aspect that distinguishes it from something like Oblivion. Or how Everything Everywhere All at Once has a scene about someone giving up the life they had to emigrate to another country and the feelings that came from that which a standard white dude won’t feel.

Edit: Sorry, I missed which community this is. Feel free to remove my comment if it’s not appropriate.