Comment by safety1st
If we're being candid I feel like brutalism for websites is more of a meme than a design theory. It's almost an anti-design theory ("hey all our modern design theories have just made websites crap, so why don't we throw those theories out").
brutalistwebsites.com seems to interpret brutalism as "I use monospace, maybe I'm monochrome and I don't need to put much on this page."
My own idea for what brutalist web design should be: "I have one good CSS file which I include in my project. It looks fine and now I'm done worrying about the design."
Brutalist architecture is about showing the bare structural elements without any decoration, so I think there's an argument for any CSS being UNBRUTAL. Which covers some recurring themes in brutalistwebsites dot com but sure doesn't cover all the "I liked the way Raygun looked but I didn't like all those itchy decayed fonts, gimme a nice clean Helvetica-wannabe please" screenshots I see in there. Just the people who said "web design went precipitously downhill the moment someone tried using a table full of images to control the page design".