Looks like a fixed width still. And that is what this thread complains about.
How does the screen look like when you change the Chrome zoom factor to 25% simulating a screen with >4000 pixels? Is just the middle of the screen being used or the full screen?
What happens if you change the font size of the browser to be twice as large or half the size?
The beauty of HTML is that it renders sensitive to the device. You might have a 2000pixel resolution but on a tiny 5" phone screen where the fontsize would be 20 pixel. You might have a 40" screen with fullhd resolution. You might print a page with 20'000pixels resolution. You might have a VR glass and read the text from there.
With a fixed width and fixed font size approach (the latter you can't even control) this effectively does reverse this advantage - suddenly it renders on one single screen resolution nicely, a resolution just 20% of the viewers have.
I would suggest to use wikipedia's layout as a reference. Try above changes, zoom in, zoom out, change font sizes, make browser window smaller,... with any wikipedia page. The result will always be a nicely formatted page.