I agree -for the most part- and I've written whole lectures about the matter. But I differenciate 'average' and 'mediocre' - it is not the same. I don't believe being average is bad per se - some people are happy with it, or don't have a unique characteristic to share or a unique path to pursue. Being mediocre though, and especially by choice, that is really sad!
Personally I don't consider myself average or mediocre although...I don't excel in anything even though I'm very good to a lot of stuff. I guess at some point it is also a matter of perspective...but that's why they say that simple people are happier - because they don't chase perfection or at least uniqueness in anything... [and that's why I probably never will be, as expected...]