Been using Elixir / Phoenix as well, and it's been a breath of fresh air. That said, I'm glad that rails has been looking at projects like Phoenix for inspiration as it continues to grow and adapt.
I'm glad that rails has been looking at projects like Phoenix for
inspiration
Other way around.
Phoenix was explicitly inspired by Rails and founded by Rails core members. Elixir was first created by a Rails core member. Phoenix is the performance-really-matters successor to Rails.
You're talking about the original inspiration for Phoenix, while the previous poster is talking about some of the new features in Rails 5. They've both influenced each other.