fie is built on action cable, and it is true that action cable has issues scaling to a large number of concurrent clients (> 1000). However, it is important to note that not all applications grow to this level of concurrent clients.
If your application is not planning on scaling to this level of concurrent clients or has not arrived to this stage yet, then your performance should be smooth.
If, on the other hand, your application is scaling to such a large number of concurrent clients, there is a solution for you. It is called anycable. anycable will give you the memory consumption and publishing speed of Erlang and Go at scale while not requiring you to change your code. You only need to set up anycable in production, in development you should continue using action cable as it is simply easier to instantiate.