> No navigational elements (navbar, breadcrumbs, etc) that allow a user to return to the main page (which is supposed to be the "master class of human-centered design). Every click is a dead-end.
This is the web, it works like people expect web pages to work. No custom behaviors, links work like links, the back button does what the back button should. That is absolutely human friendly. If external links were supposed to open on a new page then the browsers would default to that.
> Multiple SEO and accessibility issues
Whether a site has SEO issues is irrelevant to usability of the site. It's not like they are looking for organic traffic. If I'm looking for BRK's homepage, it's easy enough to find which is all that matters from a SEO perspective for a site like this.
The accessibility issues are a concern if they actually existed. This kind of site is ideal for screen readers and while it doesn't automatically adjust for mobile, it doesn't get in the way of zoom or reader view which makes the site just fine for people who struggle with small fonts.
> The page does not contain a heading, skip link, or landmark region
You don't seem to understand why the skip links are there. In this case, there is no heading full of links you need to skip over, if you open the page and start tabbing, you are already on the first bit of content. It is better from a usability perspective than a skip link.