🤔 Well, I'd like a nicer font. But I think it's a lot more effort to choose and implement a new font than one might initially think.
For one, it needs to be a font that will appeal to a large portion of the userbase. Ideally, lots of feedback would have to be gathered on different fonts. If so, various mockups would have to be created so that users can get a look at how different fonts will display in the actual interface.
Secondly, it needs to support all the languages that AOSP supports. Alternatively, only select languages could be supported, and other languages could fall back to the standard AOSP font. But that feels a bit... unfair.
Thirdly, it would mean that more future work would be spent on quality assurance of the user interface, to ensure that the font displays fine in new menus, on all supported devices, and in different accessibility display and font sizes. I'm assuming that this kind of testing has already been done by Google's QA testers, using the default AOSP font. With a new font, that QA would then become the work of GrapheneOS. I have worked in QA, and know that certain fonts and font sizes will cause cutoffs for different languages – mostly because words and sentences can tend to be longer in some languages compared to the languages that developers use when they do their own testing. That ought to be tested as well.
(By the way, from using PixelOS, I can observe that it clearly uses a different font compared to AOSP. I think it's likely under a license that prevents GrapheneOS from using it, but that's a guess).