For statically typed languages, implicit arguments (in some form or another) are really great at getting statically checked ad-hoc polymorphism.

But even in dynamically typed languages such as Clojure, ad-hoc polymorphism mechanisms bottom out at some form of implicitness at runtime. I assume you're referring to multimethods here (which generalize protocols, whose very existence is a performance hack akin to atoms vs volatile, so I'll focus just on multimethods)?

The entire lookup system based off of defmulti is really just the same thing as Scala's implicit system just at runtime rather than compile time, but even harder to understand IMO because it can change wildly at runtime. The same "spooky action at a distance" problems can result here.

The reason this isn't an issue in Clojure is that multimethods are very rarely used and instead a lot of code just specializes on vectors or maps (again going back to my point that you usually don't need ad-hoc polymorphism).