As a webdesigner this is something I subscribe to, with one exception: websites where falling out of the norm in a certain way is part of the point that needs to be communicated (e.g. an artist portfolio).

The ML in HTML stands for "markup language". Too many frameworks produce garbage markup, which is why for typical CMS systems I write my own themes that use HTML as it was intended to be used.

One of my favourite German hacker/nerd blogs uses more or less the browsers defaults for ages now and it is so blazingly fast that it is my regular "does the internet work"-website: https://blog.fefe.de/