I'll still die on this hill, but I think that the reason there's a computer literacy problem is because we moved away from following OS conventions (when they existed) and into bespoke, branded UIs for everything, and then eventually to web where every site and webapp behaves differently.

In the early days, if you learned the OS, those usage patterns and skilled transferred to every app on that OS. They all looked roughly the same, shared the same menus, shame shortcuts, same icons, etc. You didn't have to learn how to use Apps x, y, and z. You just had to learn Windows (to an extent).

Then marketing got involved, and then the web, and then suddenly every piece of software had to stand out and look and behave as unique as possible, throwing years of HIG research out the window.