For the most part things these days are all "stuff on your screen is stuff running on your computer" or "stuff in this window is stuff running on that computer"
There are definitely ways of "this program/window is on that computer / that program/window is that computer" but getting to that point requires some effort, rather than it just being "the way everything works"
With windows, or macos, or even X on linux, the vast majority of things displayed on your screen are on the computer that's within 3 feet of you, other than if you're running a "remote desktop protocol" sort of session.
The majority of things displayed on my screen are in a datacenter, which is sending rendering instructions to a window server on my desktop. But now the rendering instructions are in Javascript and the window server also browses hypertext.
I find Windows Remote Virtual Desktop to be pretty useful for running remote things. I'm sure it's just RRP under the hood but the UI integration is nice.
Right -- but the notion that each window on your system is managed by some random process running on a random remote system, and it's all seamlessly integrated, is just not a normal idiom today.
You can run a remote window in an RDP session, etc, but it's different from X where the server may be the only processing running on the system you're sitting in front of and everything else is a melange of remote systems. Even a chromebook -- the UI is driven by stuff on the "local" computer.
With X, I can run a window manager on one host, and a mixture of random windows spread across as many remote hosts as I have open windows. Plan9 is similar, but for every other modern GUI / OS setup there's a "local first" mind set. Sure, you can do things in a totally different way but those are largely the exceptions.
There are definitely ways of "this program/window is on that computer / that program/window is that computer" but getting to that point requires some effort, rather than it just being "the way everything works"
With windows, or macos, or even X on linux, the vast majority of things displayed on your screen are on the computer that's within 3 feet of you, other than if you're running a "remote desktop protocol" sort of session.