Some additional styling / colouring would seem to go a long way to help aid readability and the separation of posts and different elements on the page. Everything (text mainly) is all far too similar to each other. Scrolling through a topic, everything just seems to blend together... in stark contrast to the old forum, where skimming through a page full of posts felt (comparatively) easy. I'm not trying to be a jerk here, but it feels highly ironic that this twitter thread was getting attention on places like reddit and HN today, the same day that this new design (which appears to mostly follow the new "modern web" design trends that this twitter thread is arguing against) went live on Vogons. Heh.
Dislike of the dithering has been mentioned already, I agree. Page numbers on forum topics listing page, also extremely nice (or at the very least, an additional link/icon to take you immediately to the last page of that topic).
The old style had breadcrumb navigation links on the top and bottom of each page to allow you to quickly navigate elsewhere without having to scroll back up to the top or just click the "back" button in your browser. For example, if I am reading a post and reach the bottom and want to go back to the forum index, on the old design I could click the link for where I want to go from the navigation breadcrumbs located conveniently on the bottom of the page. That is gone now and is mildly annoying.