That was an interesting video. The late sixties was an amazing time to be working in the tech industry ... Bell Labs, the other national labs, NASA, the tech universities, etc. It was such a different environment (fostering technology development) compared to our "service economy" approach today.
The video also makes it apparent how dated the UNIX design is. Many of the UNIX fundamentals (everything is a file stream, pipe all your data around between snippets of code, scripting everything together) made a lot of sense and solved a lot of problems in the environment of the late sixties -- when everything was text based and command driven, and all computer users were trained technical users. Those concepts of computing don't fit well into modern computing -- GUIs, events, non-technical users, etc. UNIX (and LINUX which followed the same model almost exactly) has tried to adapt by patching things on here and there, but that has produced a system that is still really suitable only to technical users that are largely working the same way they did three or four decades ago. (I admit that I fall into that category at times.) For the average user, it still ends up being clumsy and awkward. Certainly Windows has its crusty corners too.
I guess a half century down the road it's time for someone to start with a clean sheet and build a modern OS. Lots of people are throwing ideas around out there (like MSR). We'll see if anyone is willing to really make the leap and build a product. MS will probably just evolve Windows. Linux (i.e. Linus) has little reason to start over. Apple? Who knows? There aren't many little guys willing to compete with the big players anymore. You invest a lot into a project and get sued or swallowed.