"Unix" missed the popularization of compute not once but twice, first with the infamous "linux desktop", then with the mobile revolution.
There does not seem to be a technical reason why this "completion" has not happened. The history of computing is idiosyncratic, very far from exploring the phase space of possibilities, let alone converging on optimal ones. Random economic and regulatory/political constructs helped fill the gap in all the abominable ways that dominate today's landscape.
Yet Unix 2.0 - the human-centered version is just a finite number of keystrokes away...