Plan 9 was built with the observation that high-resolution, bitmapped graphics displays were ubiquitous, and there was little motivation to keep the dated "tty" model as a basis for interaction. So you're expected to a graphical interface for working with the system, but it doesn't _need_ to be `rio`.
> Plan 9 was built with the observation that high-resolution, bitmapped graphics displays were ubiquitous
My impression is that Plan 9 was a child of the technical workstation age - when we thought that the endgame was having ever more powerful desktops who did most things locally and connected over a network to send and receive files. In the end, our desktops and laptops have been fast enough for the past decade or so, while servers are becoming increasingly more like the mainframes we thought had their days counted and a lot of the heavy lifting is done remotely. A lot of what I do includes firing up a surreally large cloud machine, run a couple data transformations, and then unceremoniously delete that big workstation (that's actually a small slice of a humongous server). And, the rest, is mostly applications running on what I assume are clusters of cloud machines that expose an HTTP interface to my browser (a lot like the beloved 3278 terminal, but not nearly as clicky and tactile).
Plan 9 definitely wasn't built with the thought that the endgame was ever more powerful desktops doing most things locally. "Connected over a network to send and receive files" is only technically true, yeah it's all around the 9P protocol which is a filesystem protocol, but it's a world where everything is a file. A window on your screen is a file. A CPU is a file. And app is a directory with files in it. The Plan 9 vision is all the things you describe, but more seamless. Firing up a a surreally large cloud machine isn't starting a VM with its own separate OS and configuration, it's connecting to a cloud CPU and your tasks transparently running on it. Mostl applications running on a cluster of machines that expose an HTTP interface to your browser are instead applications running on a cluster of machines that expose a 9P interface to your OS. Your impression of "the endgame was having ever more powerful desktops who did most things locally" was the Unix trajectory, and steering away from that was the big departure of Plan 9 from Unix.
Plan 9 was built with the observation that high-resolution, bitmapped graphics displays were ubiquitous, and there was little motivation to keep the dated "tty" model as a basis for interaction. So you're expected to a graphical interface for working with the system, but it doesn't _need_ to be `rio`.
I wrote a bit about this a few years ago: http://pub.gajendra.net/2016/05/plan9part1 (I guess I should get around to actually supporting HTTPS here....)