It just feels very empty and characterless. The gray background and white foreground separated by thin blue lines (:the-pigs:) gave the page definition and a certain old-school flair (I especially miss the blue gradient for the Article/Talk/Read/Edit/View History buttons at the top - it felt like something from a simpler time before everything got flattened out and material design'd into oblivion). Now the article text just looks strange floating in a sea of white, like the left margin has just been made gigantic for no reason.

Also, while it's nice to have the table of contents more readily accessible no matter where you are in the page, hiding the old sidebar behind the sandwich button is lame as hell