This is the case now: browsers are scriptable and every major browser has the ability to install extensions to adjust nearly every single feature of a page's text rendering with just a few clicks.
Turns out most people just don't care about typography.
There are just two little config changes that obviously no-one would ever care about that make a lot of newer websites unusable: Setting a minimum font size and/or forcing your own default can cause text to pile up, grow to insane sizes, screw up column width that content becomes a tiny ribbon, or cause text to render entirely offscreen. One of the main causes is the same kind of control freak design that insists on low-contrast text - designers who want some kind of pixel-perfect "responsive Photoshop" that ensures no user anywhere can deviate from their choses appearance. The other is forced fonts including icon fonts - designers are not better at figuring out what fonts a user finds most readable (especially those with poor vision) and icon fonts require turning off the users fonts and often enabling javascript.
