You could call his a civilizatory demand. Compare modern UX to this, it's more like, "here's your hand, use it for everything, just try, don't think about it (we won't make you think, promise)." Which might be closer to what figures as "medieval barbarism" in the article.
Also, the bit on the "Mother of All Demos" may be a bit unfair: The system relied on multiple users' views rendered on a single screen and respective portions of this being relayed to the user via CCTV, and, for this particular event, input and output were miles away from the machine that ran the demo, connected via a network bridge. Modern videos on social media showing a person manipulating their smartphone can be messy in appearance, as well… (On the other hand, Engelbart's real ambition, the "bootstrapping" process of symbol manipulating minds and symbol processing machines elevating each other to levels never imagined before, a project very much civilizatory in nature, probably never became a reality. And this may be due to interfaces, which teach us how to think about this process and the systems involved.)
Edit: Another early "civilizatory" approach may have been J.C.R Licklider’s "Man-Computer Symbiosis", where human and machine meet on a shared, common ground (the interface), instructing each other by suggestion, thus eventually reaching a goal of refined understanding and problem insight.
One could argue that children are "barbaric," but I really don't think it's useful framing.
Edit: One notable "relict" of Engelbart's project is the outline view in MS Word (which, out of context, may not appear to be that remarkable, while it was much about how texts should be organized and understood).
Now that needs a citation, and embeds a whole bundle of assumptions in itself. It's necessarily true, because the rich decided what "refined" meant and defined it as what they did.
But primary record from many times and places show this sort of disgust going both ways. A lot of "uncivilized" behavior has been direct response to material conditions, and "civilized" or "refined" behavior was defined in opposition to those needs. The classic example is bathing: if you spend your time up to your waist in clay forming bricks, you're gonna need to wash it off every day. A clear way to signal that you don't do that is to not bathe.
From the perspective of wealthy city dwellers, I'm sure the habits of rural serfs were disgusting. On some specific habits I'm sure I would agree. But that they were generally, across time and place, more disgusting than the wealthy? mmm idk.
But unfortunately, this feeling is fragile. The requirements are stricter than mere politeness. E.g. latency is very important. Any kind of delay (including animations) breaks the feeling of software being part of your own body. There is already a built in delay/animation: the movement of your own fingers. This is the only natural delay. Any additional delay on top of it breaks the connection between tool and human body, and and removes the feeling of merging of the two.
And any kind of automatic behavior breaks the feeling. I'm opposed to autosaving, because it's a reminder that the software is not literally a part of my body. It's better to cultivate a habit of manual saving. Predictability is as important as responsiveness. Tools are not "smart".
I've never felt this kind of man/machine unity from a mobile UI. Maybe it's possible in theory, but touch screen UIs focus on dragging, which makes latency even more obvious, by translating time delays into spatial displacements. And it's only possible with experience, which designers constantly fight against by making UI changes. It's likely that the majority of computer users have never felt it at all, and that is a real pity.
