To be frank, it's kind of embarrassing if an entry-level Windows laptop with a decent integrated GPU handles this without much effort.

Apple is free to make its own choices on priority, but I'm disappointed when something that's considered the pinnacle of creative platforms sporting one of the most advanced consumer processors available can't handle a slightly different resolution.

Nope, no windows laptop will render to an 8K framebuffer then downsample that by 2x in each direction to display it at 4K. That’s what the OP is complaining that MacOS won’t let him do.