I agree that a lot of the use cases back then were hyperspecific and the software were drag racers. However, much of what he talks about is productivity tools. I believe those fit the same description. I occasionally work with many different screens using a TN3270, some of which look very different and have very different purposes, however they have a common interface with similar keystrokes. This makes navigating even unfamiliar screens a breeze. He talks about is the commonality of keyboard language compared to that of GUI and I think that is an excellent point of his.

Check out this specific part of his postings: https://i.imgur.com/Roz80Nd.png

The main idea I got from his rant was that we have mostly lost the efficiencies that a keyboard can provide.