I changed it to "Javascript framework" to stop triggering the JS devs here, while making the identical point: if you specialize in a technology that was invented last year, you are taking a big risk that it won't survive. If you pick a technology that has been in active use for over 20 years and is currently popular, you are taking less of a risk. This is harder to do, but like many things that are hard, the reward is higher.
I really wish it were possible to make reference to JS in a less-than-glowing light without being downvoted, but alas. Substitute any other brand-new technology for "Javascript framework" if you're having difficulty seeing the argument.