Let me add my thoughts: Yes, you need to be good at JS and Node.js but to get there is easy. Maybe these thoughts about JS and that you have to be really good at it come because most of the people who know JS are rather people who fiddle from time to time with JS in the frontend using jQuery doing some DOM stuff (like me before). So, yes you need to know more than that.
But: to get there is from my point view much easier than getting good with i.e. Ruby and Rails. Just because you can build a blog in 15 minutes doesn't mean you can program with Rails after 15 minutes. Ruby is heavy (and not consequently more innovative than JS), Rails is ultra heavy with all the conventions you have to learn. In contrast, JS is a sophisticated, modern language and understanding its core concepts can take a while but in total it's more compact regarding the knowledge you have to learn. After getting into JS you need maybe one or two days to get into Node and Express. And little things like the npm surpass the rvm/rbenv/Bundler struggle by far (npm just works, period). Alone the npm is worth trying Node: its elegant design paired with Node's modularity are unmatched.
I was much earlier productive than with Rails since Node/Express forces you to think yourself about structure and this makes your more powerful, more smarter -- and just faster. Instead of learning convention after convention you just think about how to code which is much more fun as well. Besides, JS' built in data structures (in particular JSON) and design patterns are amazing and showed me that classic OO maybe isn't aged but very often overcomplicating simple things (the web is not all about CRUD and even then Node is a great answer).
Since I don't know Python/Django very well I can't draw a comparison here.