@wyatt @hatzka If I had to guess, these fundamental changes have happened since the XFree86 era:
1. Internationalization: Personal computer use has expanded out of the Americas and western Europe. Asia in particular brings a need for large glyph sets, contextual glyph shaping, diacritic stacking, bidirectional writing, top-to-bottom writing, and antialiasing to make small curves easier to distinguish. How well does X11's font paradigm handle these, as opposed to relying on "modern" toolkits to shove bitmaps around?
2. High density: People expect things to appear the same size on more than one display connected to one computer even if one has more pixels per millimeter than the other.
3. Privacy: Computer networks have become much less trusted over the past few decades. There was demand to deter publishers of proprietary applications from surreptitiously activating a keylogger or screen logger to exfiltrate your data in other applications.