It's hard for younger programmers to appreciate how different things once were.
Amen bro. But I would add how to do well with less.
To me, the marvel of V6 was how complete it still is. Other than the lack of a networking stack, and multiple windows/screens, much of what I still do day to day as a programmer can be done with 6th edition. I'd miss Go and some of the original features of ANSI C, but the editor's we had got the job, there was even a video version I was happy with. I used troff to make slides instead of PPT. I guess I would miss a Chrome and Gmail, if I have to go back to MH/HM for email.
FWIW: I just wrote a QUORA answer and referred folks to your and Brian's original book. Someone wanted to know as a beginner the 'best way to learn Ubuntu.'