> Monad is a weird type that a lot of languages can't properly represent in their type system.
While true, a lot of FP-inspired libraries in the majority of languages that don't have HKT will just implement one or several specific monads as well as the common operations on them. This creates some redundancy and slight inconsistency, but often the shared vocabulary is still strong enough to carry around expectations more or less, even if it's not explicitly enforced by the type system. That's how you can have sequence(): List<Either<L,R>> -> Either<L, List<R>> in e.g. Kotlin, for example.
Even in Scala, where you actually can define a monad typeclass (trait), there are very popular libraries like ZIO that effectively give you a monad without actually adhering to any Monad trait. I believe they do this for type inference reasons.
While true, a lot of FP-inspired libraries in the majority of languages that don't have HKT will just implement one or several specific monads as well as the common operations on them. This creates some redundancy and slight inconsistency, but often the shared vocabulary is still strong enough to carry around expectations more or less, even if it's not explicitly enforced by the type system. That's how you can have sequence(): List<Either<L,R>> -> Either<L, List<R>> in e.g. Kotlin, for example.
Even in Scala, where you actually can define a monad typeclass (trait), there are very popular libraries like ZIO that effectively give you a monad without actually adhering to any Monad trait. I believe they do this for type inference reasons.