It was the transition of commercial printing technology from "hot lead" typesetting machines (big brothers of the Linotype beasts I helped maintain while in college) to photo-offset, during which the fonts Knuth loved got "left behind" (as so often happens as proprietary tech evolves), that led him to write his own typesetting system. In the early 90s I used both vde with troff and TeX through grad school on a Kaypro 1 running CP/M. TeX was definitely the superior system for the kind of research papers I was writing (Chicago Style cites, mixed Latin and Greek text, annotated bibliographies).