Big picture this is a good reminder when the next big thing comes along <cough>React</cough> but he forgets where we came from. Prior to Angular, the major way of doing web-apps was with rendered templates that would replace whole swaths of html and so the "updating the DOM" step truly was more expensive than the Javascript driving it. This is the problem that Angular (and newer) frameworks/libraries sought to address.

But there's one more consideration...isomorphic rendering. If a framework can be rendered on the server-side then the time-to-interaction only matters if it's longer than it takes for the user to mentally process the page and take an action.