I'm talking about Shannon Information specifically. In which case, acres of whitespace and gradients very much are information. Calling them "whitespace" and "gradients" is a significant act of compression in and of itself.
I understand your argument, but even then I don't think it's quite right; there is lots of room to improve on the size of a webpage vs its rendered pixels on the screen, even with the fancy fonts and gradients and animations. I still don't believe it's really megabytes. Have you seen 4k demo contests, btw? https://www.youtube.com/watch?v=0w_xEUoK79o