Removing this part of the css fixes the problem:
https://github.com/marko-js/website-next/blob/3472afb418a822517decf0cb32e6b4e33f672dda/src/tags/app-menu/app-menu.style.module.scss#L149-L173
I figure the problem is the transform / animation, as they don't behave well with subpixel AA or AA in general.
Tested on Chromium / Linux. Difference is very noticeable on a regular full hd monitor.