[wonderzombie]

As other commenters have said the point isn't the eliminate complexity. Some problems are actually inherently or irreducibly complex! The goal is to find ways to manage the complexity. Abstraction barriers are a trivial example[0]. Type systems are another approach, hopefully foisting the complex management of datatype correctness on the compiler rather than the programmer.

None of these approaches necessarily make the problem itself less complex. But as with a type system there are ways in which a language can help, or hinder. A language which adds too much complexity incidental to the problem you're trying to solve is an example. TFA is groping towards this point, but they did a poor job arguing it.

The proposition is that a functional language's abstractions, conventions, and patterns may make it easier to manage (not dissolve) complexity. It's hard to argue that (e.g.) functions which are referentially transparent are easier to reason about, for instance. Whether this is more difficult in the large, as a project scales, is unknown to me.

[0]: http://mitpress.mit.edu/sicp/full-text/sicp/book/node29.html