Is this even true? I know some folks who have (or had) trouble programming a VCR, but most didn't. So, aside from amusing anecdotal evidence, on what is this claim based?

The book A Small Matter of Programming suggests that people adapt quite readily to assorted complex systems (e.g. knitting patterns, baseball box scores) given a proper context.

This is not to argue for complexity, but that people will raise to the occasion if they think it worth it. Don't sell your audience short (but don't make things harder than they need be).