I have a 40in monitor, a 13in monitor, and a 7in monitor.
It's impossible for a site developer to know how much space to allocate to their page.
On the 40in screen it would be asinine for me to maximise it, for example.
It's completely unsurprising to me that I can resize the window into a state where the website becomes silly. I just don't do that.
Resizing a window is trivial, it's not that you can't, it's that you won't.
edit: Obviously I know what responsive design is. I'm on Hacker News. The author hasn't done it (probably because they have better things to do), you have a trivial option to work around it.
The contrast to be drawn is with a site like Medium that deliberately goes out of its' way to be annoying and harder to use for some vague profitability goal.