Yes and no.
I think you're over estimating how IT literate my wife and many others are. I bought her a MacBook because she used to shout at the PC too much.
And it's not just her. My mum wouldn't get a Mac as she didn't want to have to relearn Windows. My aunty had Linux installed by one of her sons on her PC (for security reasons) and couldn't do a thing (another one returned it to Windows so she could go back to reading her mail and looking at the funny things her friends sent her). And before anyone asks about how all these examples are about women, my father is so IT illiterate I can't even form a coherent example of his lack of knowledge because there's so little of it (though he still surfs the web and looks at his photos).
For these people the idea that you'd go and look for an alternative is a pretty big stretch and that's before you ask whether they actually have the skills to carry out a proper assessment of what is available, what meets their needs, what's robust, what's actively developed (a major consideration in the FOSS world) and so on to make a choice. And even if they do do all that suddenly a major part of their world changes and there is (for them) a major investment in relearning how things work.
If you've got the skills and genuinely worry about these things then I agree FOSS is great but for a massive, massive number of people they just want something basic that makes some sensible choices they can live with and get on with doing stuff. Right now that's a need FOSS is doing little to meet.