What led you to think that Ruby devs don't know the basics of Javascript?
My last sentence on the parent message was directed to the comment I was replying to (which said they couldn't set up node properly).
What I do think is that there's a huge % of Rails devs that hate on JavaScript as if it were some kind of enemy to beat or something, and often that leads to people not wanting to learn it properly.
Luckily, I no longer need a PhD in webpack or node packages in order to run rails s successfully.