I disagree strongly w.r.t. Python as anonymous lambdas are heavily restricted there. I disagree less strongly but also somewhat insistently about Ruby where the distinction between methods and functions is warranted but thus involves more overhead.

Having to use "def" isn't the end of the world. You often end up naming your lambdas in a let in scheme anyway.

JavaScript is hospitable enough that you see entire applications written in a functional style. Where is the Python and Ruby applications written mostly in a functional style? I've never seen any.

I've yet to see entire JavaScript applications written in a functional style. Just because "map" is used more often than Python doesn't make it functional.

I'd agree with this point. I don't think Python, Ruby, or Javascript are particularly "functional", whatever that means.