Perhaps the key isn't to focus on specific languages, libraries, or frameworks, but on what you're building and the problems you're solving. You can learn this as you learn new tools, but the key is to keep your eyes and ears open to these details as you go.
> For new kids its easy, you just pick up the latest thing
I think it's actually hard for them because they don't really understand what the new thing is, why it is, what it does, etc. Sure they can learn the ropes quickly because so many modern tools have such ergonomic development experience, but they don't actually know what's under the hood beyond lots of code.
That touches on an important thing to learn, which is the "why". New developers often understand the why of things — from languages, to tools, to features, to entire applications — in a very limited and superficial way. It doesn't often change much, though. You can see underlying patterns and conventions that have spanned decades in various forms, even in newer tools like React. And really, React is dramatically easier to learn once you understand what it's doing and why. You'll fight with it less because you know what does or doesn't make sense to do. For example, you won't try to couple imperative code with components, because you know declarative conventions make much more sense. You won't litter props with inline functions, because you know the function references will never be the same and reconciliation will never be ideal. These lessons will come with you, because the code driving all of this uses common, fundamental, truly useful patterns you'll encounter elsewhere.
The more you can learn why things are the way they are and how things work, the more you'll see that these underlying reasons have significant staying power. Understanding this stuff even makes it a lot easier to adopt newer technologies; you can anticipate how you're supposed to utilize it, and why.