Doomed is a bit of a strong word. I personally prefer static types because they reduce the number of unit tests I have to write, and at a higher level (followin

Doomed is a bit of a strong word. I personally prefer static types because they reduce the number of unit tests I have to write, and at a higher level (following from this) they can inform the design of a system in a way that encourages robustness. Algebraic data types are not really inherent in functional programming at all; as you mention you can do it just fine in a dynamic language and a good chunk of ADTs and type stuff translates to say Rust as well.