It's very easy to ignore the cruft with JS, and opening up the console and typing some code and having a graphical playground makes it ideal to try things.
Python and Ruby are not in the same category IMHO, and while they are extremely good at what they are designed to do, I doubt that they could reach the lingua franca status js has. I would evaluate JS with PHP, Bash and C together, and I know how weird that sounds.
Lingua franca "language used as a means of communication between populations speaking vernaculars that are not mutually intelligible."
Javascript is too Web focused. Python and C are better candidates as they are more than Web.
Python and Ruby are not in the same category IMHO, and while they are extremely good at what they are designed to do, I doubt that they could reach the lingua franca status js has. I would evaluate JS with PHP, Bash and C together, and I know how weird that sounds.