Low quality but high resolution do not do good together, it's like minecraft of pixelation when you click to expand to true size. I tried to fix this image with gimp and even used gmic, this couldn't have been made worse pixelwise if you tried to do it. In the future I'd use a low resolution with a high quality filter to push and image. I'd also export as a png and not try to lower the file size for the internet with compression since that basically is making an image shitty for the internet in my book.