It arguably depends on the syntax.

In an ML-like syntax where there aren’t any delimiters to surround function arguments, I agree it can get a little ambiguous because you need to know the full function signature to tell whether an application is partial.

But there are also languages like F# that tame this a bit with things like the forward application operator |> that, in my opinion, largely solve the readability problem.

And there are languages like Clojure that don’t curry functions by default and instead provide a partial application syntax that makes what’s happening a bit more obvious.