Hi, I am not technically knowledgeable in the subject of font rendering, but as someone who suffers from astigmatism, font sharpness and fullness is very important for me. So I usually set up my GNOME desktop to use a semibold font to mimic the highly praised font rendering from MacOS. It doesn’t actually need to be thick bold which becomes ugly, but rather semibold or medium is usually fine.
For some reason, choosing a semibold font via GNOME Tweaks doesn’t actually render them bold, for instance in the Shell menus or Files. The font weight must be set via gtk.css in ~/.config/gtk-3.0 and ~/.config/gtk-4.0 for the boldness to be properly rendered.
I show two screenshots of my GNOME desktop (openSUSE Aeon if it matters) using the same Source Sans Semibold font, one with the font weight set to 600 and the other without. If you notice, without font weight the fonts look noticeably skinnier. So this setting really helped fonts to look sharper and fuller across the board, in the shell and apps.
My suggestion is that either the default GNOME fonts are set to have an increased weight or an accessibility setting is introduced to allow this to be enabled by the user.