Ultimately it appears to be software with more fans than productive users.
I love the idea of arcan, I like how as a counter point to waylands "X went to hard, the display server should be a dynamically linked shared object" there is one solitary guy doing his own thing saying "X did not go hard enough we need an even more seamless, recursive solution to move our display between different devices" and doing amazing work on this problem.
But just like plan9 I have a hard time actually doing anything with it. Achingly beautiful software, but just a little to different and obscure. And I say that as an OpenBSD daily driver, where apparently I thrive on the pain that comes from using an obscure system.
But I am currently back on the plan9 kick, seeing if I can get it to stick this time. I may give arcan another try as well.
Even the style of writing screams "I'm doing something weird and I'm not going to explain it to you unless you are already a mega-fan". Reminds me of Wolfram's writing a bit. He's created a world that only he is in and then writes about it in detail as if everyone else is there too.