Most of my nostalgia and pet peeves have already been mentioned at least once in this thread, but the only thing I'm shocked that nobody's brought up yet is the absolute blight on the face of the internet that is infinite fucking scroll.
Gee, the one thing I always wanted from my long-form browsing experience is to have to start at the very fucking beginning of whatever I'm reading every time I click away from the page for any reason, or perhaps when my browser crashes because it was forced to keep every single page of the site loaded at all times! I guess actually wanting to view the content on offer is a lot less important to our shiny new web 2.0 experience than having the most stylish, slick, modern, and minimalist design around. Or maybe it's that clicking a next page button to see more was deemed too complicated by our tech overlords, and adding fancy javascript to replace one of the web's most basic functions, with a version that makes it far less easy and convenient to actually use, was just "better" somehow. It's basically the web design equivalent of the earphone jack removal in phones, and I fucking hate it.