That is precisely the kind of insistence that prevents people from adopting functional languages for real world programming tasks.
JavaScript certainly lacks language level support for function composition, but it has the basic tools to allow you to build combinators and compositional functions yourself, and when dealing with functions as data you often find you can elegantly refactor code by building such a thing - so in terms of 'learning about functional programming' JS can be a great workbench to help procedural minded programmers discover those tools by discovering and building them.
So maybe JS doesn't teach functional programming, but it does at least introduce you to paradigms from which it is possible to see the benefits of a functional language.
Of course, if you then hear that those languages are only for doing math in then you'll stick with JavaScript.