Mobile supplied an acceptable device for doing most things a non technical person wants to do with a computer. This killed the advancement of technical competence but I'm not sure it set it back much. There have never been that many people who really get computers beyond the UI. Most people don't know how to fix a car either.

That being said, I do hate on mobile often for being closed and locked. PCs could provide a friendly UI that led people gently into more tech savvy levels, while mobile seems to lead nowhere.