Without support from Rails, all of these libraries unfortunately can't be used by 99% of Ruby code out there and using Ruby in any sort of fan out architecture remains a pain (ie almost impossible in practice).
I haven't really had time to explore the usage of Polyphony in Rails apps. Personally, I don't use Rails in my work, and instead develop custom Ruby apps. I believe there's a place for Ruby development work without any connection to Rails.
This is where the "in practice" part comes in. Ruby culture thinks it's a great idea to use global mutable state in lieu of request local state all over the place because the code looks so beautiful if you don't have all of these parameters and just grab stuff from the ether. So unless all of your dependency tree (three quarters of which probably had its last release in 2017) fixes their usage of global variables, you won't have much fun even if Rails itself got rid of their global variables (to be fair, they've done a great job over the last year or so).
> Ruby culture thinks it's a great idea to use global mutable state in lieu of request local state all over the place because the code looks so beautiful if you don't have all of these parameters and just grab stuff from the ether
That is utterly incorrect. Make it s/Ruby/Rails and you'd be somewhat more correct. Cue Rack, Sinatra, Hanami, Roda, and that's just web "frameworks".
> all of your dependency tree (three quarters of which probably had its last release in 2017)
I don't see how that could make sense. Some libraries can be mature and thus not warrant much, if any, update.
Also, the aforementioned pattern is only present on a small subset of Ruby gems, usually ones that are close in mindset to Rails.
Nothing prevents anyone to code in Ruby in a functional-like style, nor pick dependencies that are written with such sensibility. But if you wilfully pick Rails you can't really expect to veer too far from the philosophy that comes with it.
Because eventually a dependency will make it non concurrent.
Rails is the driving force for adoption in the ruby ecosystem. If it isn't a rails requirement to be concurrent friendly, it will be broadly ignored.
