> "Why is it so hard to configure my phone to only allow my friends to interrupt me at any moment of the day, rather than any rando?"

https://play.google.com/store/apps/details?id=com.vladlee.bl...

Also, some Android phones seem to allow you to block calls from unknown numbers:

https://community.ee.co.uk/t5/4G-and-mobile-data/How-to-bloc...