It's probably been a long while since you've gone back to it, but The "Worse is Better" chapter in this book seems to show rather amazing foresight; it basically predicts the situation you describe regarding Unix being "the best operating system available without getting appreciably better" and offers compelling reasons why that was likely.
I heartily recommend his other writings. In fact, he considers "Worse is Better" some of the worst of his writings, and it is the most successful. ¯\_(ツ)_/¯
Just one that I've gotten a lot of mileage out of is "Habitability and Piecemeal Growth" in Patterns of Software. Lots of other gems in there: Reuse vs. Compression, The Quality Without a Name, etc.
25 years ago. Who the hell does that?