I find being a "builder's FP" more true of something like Rust than Elixir, in my experience. This is mainly due to the lack of static and algebraic types in Elixir, which makes debugging very difficult, as well as more annoying to reason about the problem domain, because you can't represent it in types as well.
> lack of static and algebraic types in Elixir, which makes debugging very difficult
In about 6 years of working with Elixir, I've found it easier to debug than pretty much every other language I've ever worked in. But to be fair, I've mostly been working on code I've written myself in that time (although you'd be surprised what you forget in a year and then go back to).
You can also add typespecs; I know it's opt-in, but it's something, and it will get checked.
Algebraic types are orthogonal to functional programming.
Functional Programing can be static or dynamic.
Also, Rust isn't an FP language, per say, it has way more in common with the imperative programming paradigm with some ergonomics lifted from the ML family of languages, specifically around it's type systems.
