Ewww what's with this terrible trend of wasting the majority of the screen space on a 16:9 monitor like this. Let it fit the window width, if someone needs it to be narrow let it adjust itself appropriately.
White space isn't wasted space. It makes the page infinitely more readable to limit line lengths. Yes, you could have reduced your window width before. No, you shouldn't have to do that to get a comfortable reading experience.
Making more than half the screen white space is wasted space. The point of resizable windows is to be able to adjust the content as desired, so it's pretty ridiculous to argue that everyone else should suffer wasted space because long lines are scary.