In the beginning of my experience, it wasn’t that computers had fonts so much as each computer had A Font, and that was how the computer talked to you. All of them were quite low resolution; blocky and bad.

Now I expect every character to be drawn in an appropriate, smooth, curved, and informatively differentiated typeface.

When did that change start, and when was it complete?

One thing that UNIX users have that Mac and Windows users don’t: it’s generally quite easy to change their window manager theme – and to write/draw their own.

Window decorations – a frame, a titlebar, some buttons – are handled by the X11 window manager, which is itself a replaceable part. Window managers range from minimalist exercises in reductionism through gaudy feature-festivals like Enlightenment, the original perpetrator of shaped, translucent and transparent effects. But…

Do you have an X11 application that insists on using a font you hate?

Change that easily with fontconfig.

This syntax in your .fonts.conf will change the response for one font into an answer from another:

<alias>
 <family>Gentium</family>
 <prefer>
  <family>Tex Gyre Pagella</family>
 </prefer>
</alias>

Add as many stanzas as you like; then run fc-cache and restart your application.