LISP isn't a pure functional language, it's a multi-paradigm language that is as dynamic as they come. Its problem isn't lack of expressivity, it's probably that it's too flexible (and of course the syntax throws people off).

As for Haskell, I guess that gets into the question of how you define expressivity, which is admittedly a very fuzzy term. Here I meant it to mean capable of fluently expressing many different kinds of algorithms without having to resort to circumlocution.

Functional programming is natively supported in almost all modern languages. You call a function which calls a function which calls a function which calls a function, return the result. There's no syntactic sugar, just function calls.

In Haskell, while I've seen people argue that do notation may as well be imperative code, it isn't. It's an approximation of imperative code using Church—Turing and a liberal dose of syntactic sugar, and using it effectively still requires you to understand the underlying monadic model.