It seems to me your point about KISS and the author's observations are compatible. Facebook is successful for reasons that have almost nothing to do with their

It seems to me your point about KISS and the author's observations are compatible. Facebook is successful for reasons that have almost nothing to do with their code, however, and as long as that's true there isn't a reason for them to change how they develop their software. In that sense, code quality doesn't actually matter (at least, until it does).