12 px (13.333 px when in the adapted layout) is a little small - and that's a perfectly valid argument without trying to argue we should abandon absolute sized fonts in favor of feels.

There is no such thing as a reasonable default size if we stop calibrating to physical dimensions. If you choose to use your phone at a scaling where what is supposed to be 1" is 0.75" then that's on you, not on the website to up the font size for everyone.