It’s really not. That's actually a pet peeve of mine as someone who used to spent a lot of time messing with pixel art in Aseprite.
Nobody takes the time to understand that the style of pixel art is not the same thing as actual pixel art. So you end up with these high-definition, high-resolution images that people try to pass off as pixel art, but if you zoom in even a tiny bit, you see all this terrible fringing and fraying.
That happens because the palette is way outside the bounds of what pixel art should use, where proper pixel art is generally limited to maybe 8 to 32 colors, usually.
There are plenty of ways to post-process generative images to make them look more like real pixel art (square grid alignment, palette reduction, etc.), but it does require a bit more manual finesse [1], and unfortunately most people just can’t be bothered.