A lot of those sites appear Brutalist, but open up their source and you can see they are still quite bloated. So they are just going for the look. Someone posted https://wiby.me on here regarding an article about old websites. This is an example of web brutalism, the site itself is basic but not ugly and there is practically nothing in the source that is going to slow down my machine. Hacker News is also a perfect example. Now one example from that article (https://theoutline.com/ which I picked randomly) has a 284kb CSS file in it. This is the norm, not the exception for most contemporary sites.
On my phone, I don't have much data for my plan. I have to be careful just visiting websites. Literally just visiting a few websites can cause me to download hundreds of megs...
That sort of makes sense though, if the design trend (whether you wanna call if 'brutalism' or just the form du jour), is more focused on the aesthetic rather than how it gets built. I suspect the adherents to this type of design would consider themselves designers, not developers, and thus are less concerned with bloat and file size.
On my phone, I don't have much data for my plan. I have to be careful just visiting websites. Literally just visiting a few websites can cause me to download hundreds of megs...