The first Vim commands people learn generally fall into this set: i, i_<Esc>, gg, h, j, k, l, yy, dd, p, :w, :q. But any computer literate person should be able to operate on this level in a basic "Notepad" application. The be highly productive in Vim, I think you'll need to learn closer to 50 commands.
Now, if you think learning 50 commands is hard, think about your ability to touch type: that's at least 50 keys. Think about your programming language vocabulary. Think about your English language vocabulary. (Frankly, if I lost the ability to remember more than 10 Vim commands, re-learning Vim would be the least of my worries.)
> any computer literate person should be able to operate on this level in a basic "Notepad" application
Yes, although I will say that <n>dd, p and P when properly wielded are a nice boost in power over optimal Notepad editing, even with mastery of the system-specific modifier key selection techniques.
Now, if you think learning 50 commands is hard, think about your ability to touch type: that's at least 50 keys. Think about your programming language vocabulary. Think about your English language vocabulary. (Frankly, if I lost the ability to remember more than 10 Vim commands, re-learning Vim would be the least of my worries.)