Generally just using the system font is fine for most UI interfaces and the only good reasons to change it are:
1. You have a specific branding style you need to achieve (this is becoming rare) 2. Your interface has pixel perfect user created content where the difference in font to font usage between OSes / Browsers would cause actual breaks in layouts from user to user.
I run into the later often, and so we end up picking a neutral style font like this because it's the closest thing to a generic "system font" like Roboto or San Francisco that has a friendlier license.
Personally I prefer Inter UI https://rsms.me/inter/
For print sure serifs are good but again it depends. There are many highly readable sans serifs (that have big x-height).
I would imagine tech geeks and artists are generally the people who are downloading new fonts, and those poeple are probably spending most of their time using sans serif fonts or monospace.
There are multiple needs here and it seems the only action comes from the "sexy" side of things.
* https://github.com/uswds/uswds-for-designers#fonts
* https://designsystem.digital.gov/components/typography/
* https://github.com/SorkinType/Merriweather/blob/master/READM...