Judging from the context, the user interface was fine in the days of limited resources (a 16 kiloword PDP-11 was cited) but then modern computers have the resources for better user interfaces.
They clearly didn't realize that even more modern Unix kernels would require hundreds of megabytes just to boot.
Of course, but the same (with a bit lower number of years) can be said about Windows, or HTTP, or the web with its HTML+JS+CSS unholy trinity, or email, or anything old and important really. It's scary how much of our modern infrastructure hinges on hacks made tens of years ago.
People new to the internet think alike. Still, not a day passes and we are once again reminded how fragile yet amazing this all information theory stuff is.
They learn. We all do.