The worst is the "mobile-first" approach which makes the desktop version suffers. Reddit's new redesign looks terrible on a 21:9 screen. Most content is centered on 1/3 on the screen. So much wasted horizontal space.
I'd say the redesign actually makes Reddit usable on a 21:9 screen not the other way around. I mostly browse text based subreddits so entire paragraphs becoming one long line which to read you have to move your head is more annoying. The redesign makes the site usable on more than a 5:4 or 4:3 monitor for which the original version was designed for.