I think simplicity is relative, and the first few years of WordPress were actually pretty complex.

Milan also nails it that people don't necessary want simplicity or their site to be cookie cutter. If you look at the comments on the Ghost article it is a mix of people who want simpler blogging and some who want crazy built-in post types.

I have some ideas for the post editor, though, that I think people will really dig. You can satisfy both camps, it just takes iterations and probably a few missteps along the way.