This page has some elements that scroll and some elements that don't scroll. And some elements that switch between scrolling and not scrolling. And some animations are controlled by scroll position, meaning they bounce back and forth while I try to find my bearings on the scroll wheel. Everything is fighting for my attention all at once, which prevents me from focusing on anything in particular. Most of all, it prevents me from focusing on the scrolling itself - and scrolling requires extreme focus here considering you never know what will happen and how much you need to scroll for it to happen. Is text going to slide in? Is a picture going to suddenly pop up? Is an existing picture going to transform to something else? Will it transform gradually as I scroll, or is it going to do it all suddenly in one step?

In short - it breaks the UI metaphor of scrolling an infinite roll of paper, and that in turn breaks my brain. I just can't follow what's happening, there's too much non-scrolling action happening when I scroll. There's also too much empty space between paragraphs.