Pixel art isn't just bucketing a higher resolution image into a lower resolution. If you're going to use that term, you should probably have at least a basic understanding of the medium.
Thanks for pointing that out. You're absolutely right. What I'm doing here is definitely not pixel art in the traditional sense, and I now realize the term may have been misleading. My apologies for that.
This. I wasn't expecting much, having tried similar claiming algorithms and been disappointing. But even among those, the example image used here looks barely better than downscale and posterize