But it's not new stuff, mostly. It's just the same old stuff in a new package.
Aren't you contradicting yourself?
Why? It takes time to master new ecosystems, even if what they offer is a complete duplicate of what already existed.
Yes, indeed that's true. But they get upset if you tell them that their genius new idea is just an old idea they didn't know about ;-)
That's precisely why it's not really that big a deal to learn the new stuff. If you know the fundamentals, learning the new tech is fine. It can be a little daunting at first but once you familiarise yourself with the new jargon and what value the practical differences bring you can apply your knowlege very productively.
No. Learning a new ecosystem is far more work and takes far more time than (so to speak) learning a few keywords of a new language.