I don't see anything I would not expect when exported at that resolution. Saving as an image will always show pixels.
Zoom in and you will see more. You can try to double the resolution to 144 ppi on export.
That's probably due to visual effects that depend on the coloring.
Maybe you can point out where you are seeing this by highlighting those areas?
Sorry to hear about this experience. As pointed out by Ton and Monika, saving an image in a raster format such as JPEG will result in pixelation when zoomed in. You may try saving at a higher resolution to reduce it or saving in a raster format such as SVG to alleviate such issues.
Also, kindly check the exported image on a different device to see if the problem persists and share your observations.
Looking forward to your response.
If you save as an Illlustrator AI file, an EPS file, PDF, or SVG file, the vector lines will be preserved and will be smooth.