If it seems like so many of the sites you visit are built from the same templates, that's because they probably are. The prevalence of the CSS Bootstrap framework, the rise of site creators like Squarespace, and the dogmatic prescription to complementary color theory have made web design more accessible than it ever has been, but it's also resulted in a cookie cutter approach to design.
But just as brutalism architecture upended upended standard notions of architectural design in the 1950s, brutalist web design is looking to redefine how we look at web sites. The architectural movement was couched in the theory that buildings should be functional and suited to their purpose rather than created as florid works of art, and it led to a movement towards sturdy, squat concrete structures that could stand the test of time and suit their purpose in the most efficient way possible.
Brutalist design follows a similar philosophy. It's predicated on the notion that websites should be about the content contained within, not on the artistic flourishes or the vanities of the designer. It seeks to draw back to the raw notion of what a website is. While designers and developers spend countless labor trying to create responsive websites that fit all the bells and whistles into a wide variety of devices, brutalism suggests that the more effective way to ensure readability across devices is to merely strip down the unnecessary components.