Well, we all knew it was coming. Wikipedia has changed its default skin. Here's my most surprising take of the year: I don't think it's that bad. I know I'm always out moaning whenever something like this changes, but I don't think this change is completely awful. I do have a couple of things to moan about, though.
As long as your browser is based on Blink, Gecko, or WebKit[1], it works very well. I find the more narrow block of text easier to read. The padding isn't too excessive, and most of the buttons aren't too hard to find if you're familiar with the old style. Even with JavaScript disabled, all the collapsible menus work since they use the CSS checkbox hack.
However, things get much worse when you use anything outside of the Big 3. On NetSurf, it's impossible to see the menu or the table of contents because it doesn't support enough of the CSS they're using. On Ladybird, it ranges from completely unusable to the same as NetSurf depending on the width of the window.
On Lynx, you have to scroll past the entire sidebar and some other garbage (or click the "Jump to content" link) before you get to the content. With the old theme, the content was right at the top. There were links to jump to the navigation or the search bar, both of which you would do infrequently.
As you can see, they didn't really care about anything but the top 3, and that's a real shame. Fortunately, they do offer a way to get back to the old look. If you're signed into an account, you can select "Vector legacy (2010)" as the skin in the settings.
If not, you can append useskin=vector to the URL as a query option, e.g. https://en.wikipedia.org/wiki/Wikipedia:Skin?useskin=vector. This can be automated through the use of the Redirector browser extension or something similar, but that will be left as an exercise for the reader.
It could definitely be worse. I just wish they cared more about compatibility. There's no reason why I should need a browser supporting the latest and greatest technologies to view an encyclopedia.