I don't have to use plan9 to secure the benefit of exploring models of software, systems, networks which plan9 explored.
I think that you have to swim very strongly across some currents, to decide to "be" in plan9, but its no different in that sense to choosing to live behind a Nokia brick phone, or only using pen and paper in meetings. Others may work effectively in their kanban on a laptop, but the decision to stop using the parts of your brain which type, and instead use the parts of your brain which shape semantic intent, by writing, is quite large.
And in that sense, deciding to use plan9, or even just a tiling window manager, or to disable image load in web by default, or to use Markdown or Org mode to do thing instead of reaching for some packaged electron app, or to focus on GO or Haskell or whatever the thing is, which forces you to think about what you are doing in code, That decision may be swimming against the stream, but its big.
Plan9 is big. Its not for everyone, and I decided not to invest because it had moving parts I didn't feel confident I understood and at the time I looked at it, was wedded to multiple independent instances of boxes I didn't own.
Now, it is probably entirely possible inside containers or VMs or something, but I am content to know I could.
(I am however, using pen and paper more in meetings)