It's part of our ongoing education.
A year or two ago, we were watching conference speakers and bloggers and authors and consultants sing the praises of AngularJS. It was surely the One True Framework, and if you didn't know it you were no-one. Don't tell that to anyone who's a fan of React today, though.
A year or two ago, Grunt was the shiny new tool for automating everything. Today, it's old hat, and apparently we're all supposed to be using Gulp instead.
A year or two ago, the previous Javascript module patterns and optimisers had become a plague on all our houses and we were implored to use AMD and RequireJS instead. Today, Browserify lets you use a module system bolted on to a server-side version of a language that only survived because it was the only client-side game in town on the client-side as well, and that constitutes progress.
And yet, for probably at least a decade, I haven't worked on a single commercial web development project that lasted less time than every much-hyped web technology's reign at the top. These fads literally come and go faster than any long-lived real project that might use them. They are good for demos, column inches, conference talks, and disposable MVPs that don't need to worry about irrelevant details like maintainability and still working next year.
So don't worry, Frank. Those kids you mentioned in your second sentence don't appreciate this, because they're kids and they want to play with their toys. When they grow up, they'll understand. :-)
I don't know Ruby. I don't know Node. I probably never will and I don't care. Because I can do the same type of things with Python and JS. Time is limited and I don't have it for learning redundant ways of doing the same thing (unless someone is paying me... that's different).
You should learn Git though. That's important.
