I'll take a slight different road on this topic. I think we are dealing with the paradox of progress. I don't blame Linux's developers any more than I blame BSDs or anyone else. Really it was hardware progress/Moore's law that changed the rules :-)
As much as I wax a bit for the simplicity of the Fifth, Sixth, and Seventh Editions of my youth, the truth is I would not want to try to use them today. My needs are now different and I think the is true for most people also which is why a modern UNIX implementation is different from the original ideas or maybe I should say ideal. That said, a lot of what I did then, ands like Steve, I still do use and many of the 'classic solutions' I find are better for me (i.e. troff vs. MS-Word)
Pike's 'cat -v harmful' paper foretold where we would get. On the PDP-11 with a limited address, a programmer was constrained so you had to keep things simple. The programming model of small simple programs that did one thing well, was easier to 'enforce.' The ideas that formed UNIX make sense, and yoiu could build an extremely power 'system' from simple and small things. At the time, that was almost heretical. But once HW dropped in price and the address space issues relaxed the size of a program that could be written, people did. The cast was out of the bag, and there was no going back. I'm not saying all of the new BSDism of the time were right, but they certainly made many things easier/more approachable for many users and many/most live in modern UNIX definition.
I think Ted makes an excellent point, that *BSD and Linux, by their nature of being 'open' and 'available' pushed the code along and that needs to continue to be the high order bit. Open and freely available had a huge positive effect, because many of these new feature (like X-Windows, Networking) were 'useful' and the cost to add them was accessible -- so people added them. But .... slowly the system changed and the expectations of the users with them.
I admit, I'm torn. I do think Pike was right and many of the new features/frameworks et al are pretty lame (useless IMHO) and the simpler/cleaner methods of old, are being ignored. Dave Pressotto and I were talking a week or so ago and Dave made the observation that he's not sure he knows how write a modern program now with all these frameworks, IDEs, etc and I completely agree. But that is the old guy in me talking; but I really do want to see progress and the new generation make its mark. I'm sure they will do wonderful things.
Bakul's observation of little >>practical<< progress is an interesting one. In many ways I agree, in others I'm not so sure. I think Ted knows that my major gripe with some of the Linux (and Gnu style) community has been a focus on reimplementing things that were already there instead of using what could have been taken from somewhere else such as BSD, or replacing subsystems just because they could without really adding anything (i.e. the whole systemd argument).
But over all, as much as I respect and think Ken and Dennis did amazing work at the time, I do tend to love when new ideas/things have been done beyond the original ideas from Ken and Dennis. For instance, just as BSD can take credit (or blame) or sockets and making UNIX really a 'networked OS', Sun really gave us multiple file systems with the VFS, but I strongly credit Linux for really making kernel modules a reality (yup Solaris had them, as did a few other systems - but it was really Linux that made it wide spread). I wish Linux had taken the idea of a modular kernel a tad farther, and picked up things like Locus vproc work, because I personally think modularity under the covers is better than the containers mess we have today (and I agree with Tannenbaum that uKernel's make more sense to me in the long run - even if they do cost something in speed).
it's also why I liked Plan 9 and have high hopes that a new OS, maybe written is something like Rust might finally appear. But I don't want it re-implement UNIX or Linux. Grab from them the subsystems that you need to duplication, but don't re-invent.
Warren - at the risk of being political -- I think the paradox we have it larger than just UNIX, although it is simple. We can wallow and say everything is bad, it was simpler in 1959 -- which exactly what some folks in my country seem to be doing in other areas. I personally can say my world was simple in those days and I certainly have fond memories [read Bill Bryson's
https://www.amazon.com/Life-Times-Thunderbolt-Kid-Memoir/dp/0767919378 which parrots many of my own memories of those times ], but UNIX, like the world, has grown up and changed and is a lot more complicated. I like progress we have now. I don't want the world the way it was any more than I want run Fifth Edition on my Mac for day-2-day work.
Yes, I would like us to look at the good from the past and see if we can have some of the good things again; but if it means giving up what gained too, then we have gone backwards. The problem is how to decide what was good and what was bad? What is real progress and what is just 'showing off your money' to use a Forest Gump concept.
I suspect we will argue for a long time about what qualifies as progress from the core idea of UNIX and what does not.
Clem