Basic=Simple?
Apple just announced the MacBook Neo. It's a smaller MacBook at the surprisingly (for Apple at least) low price of $599. They evidently designed this with price in mind, but it looks like the tradeoffs don't introduce any significant issues. Members of the tech press who have some hands-on with Neos have reported that the quality Apple hardware is known for hasn't been compromised. The Neo looks like a very good basic laptop.
Since the beginning of personal computers, there have been more basic systems at lower prices than mainstream or premium choices. The most basic personal computer I can think of is probably the Sinclair ZX81, from 1981. In the US it was sold as the "Timex Sinclair." It was the lowest price personal computer that had ever been seen. Very basic.
But it wasn't simple except in the sense that there were some operations that it probably couldn't perform. I never used one, so I might be wrong there. But even entering text was "less simple" because the "keyboard" was just a plastic membrane, and each "key" had several functions. You could automatically enter commands and keywords for the built-in BASIC language by using combinations of "keys." There were probably users who managed to type fairly rapidly on a Sinclair ZX, but I suspect it might not have been easy to develop proficiency.
It may be true that in the early days of personal computing, there really weren't any systems that could be called "simple." Gaining entry to the computing world had come down dramatically in price ($100! Unheard of!), but you still had a lot to learn. But most personal computer designers tried to make it simple — or at least simpler — for users. That's probably behind the design choice of assigning each "key" five different functions. Less typing on that "keyboard."
I think this shows another aspect of simplicity. Time. Using a personal computer for the first time was a completely new experience for everyone back in the day. There was a lot to understand, a lot to learn, and even some things to unlearn, especially if you were a typewriter user. Or, for that matter, a computer user at the time. No more punch cards. The Macintosh was famously designed to address some of the complexity of early systems, and it came with aids to help new users learn basic motor skills like using a mouse. Now, decades later, I think practically everybody knows about on-screen pointers, mouses and trackpads, clicking, and the rest. Now it's "simple."
Widen the time scale a lot and you can see the same effect in, for example, our understanding of the universe itself. The earth orbits the sun, which makes a lot of things as simple as night and day. It works that way because of gravity, which we understand at the drop of an apple. Now these notions are "simple," but at first they were anything but. Simplicity, like beauty, is in the eye (or mind) of the beholder.