Half of the internet is designed in this retarded way. Some sites only occupy 50% of screen width on a 1080p screen, so that's 25% on 4K with same DPI settings. I zoom into 150% on most sites as it relieves some eye strain. It's kind of strange since a lot of webdevs claim to make fluid layouts that are suitable for mobile, small and large displays. But then they are still able to produce this kind of crap. It's very annoying.
But honestly less annoying than some other website features: like cluttered navigation systems, high amounts of padding, websites that are completely decorated in ads (hmm, maybe that's why people use adblock to get a sane internet, and maybe that's why they reserve all that empty space?)..
Or shit like hover dropdown menus drive me crazy, they are the worst (goodbye accessibility for the less well coordinated among us, and goodbye usage on phone)
I've used a restyling plugin for many years with custom CSS scripts, but as soon the news got out that the plugin was infected I uninstalled it and didn't look back. Going to large efforts of customization only makes my system installations less portable across multiple machines or reinstalls, which is also something I've started to hate since it increases the effort threshold to switch systems for me (I daily drive 3-4 computers on a day).