Rust is an abstract mess that needs a PhD (or type theory or guess-and-check) to use productively; it's more to do with overuse of generics and wildcard trait impl and trait resolution and higher-order functions and lifetime HKTs and reverse type inference, than sum types. Rust enums require less generics to use productively than C++ std::variant (which requires std::get_if or std::visit), because enums have language-level `match` and `if let` syntax as a fundamental binding block which can take the place of combinator method chaining (but the community instead sees it as an opportunity to invent and add even more methods).