Overly simplified. Content Marketing started long ago with examples such as The Furrow Magazine by John Deere. While these days SEO and blogging have become more pervasive and everyone is looking for the fastest way to win, lets not think that they are they only content marketing strategies available. And thought leadership is just what John Deer achieved with the The Furrow Magazine. Your points have only managed to solidify the fact that content marketing is still solid but most people are competing for the low hanging fruit creating the illusion of saturation in the entire content marketing world.