Email has changed since [the 1970s], but not much. Most of what’s changed in the last 45 years is email clients—the software we use to access email. They’ve clumsily bolted on new functionality onto the old email, without fixing any of the underlying protocols to support that functionality.
The article is mostly about the efail stuff and how it’s apparently inherently bad that email can be HTML because it brings the vulnerabilities of web browsers to email clients. Fair point. Pretty impressive that those protocols and such haven’t changed for half a century. What’s the HTTP/2 of emails going to be?