This was the approach one of my first mentors recommended and it's served me well. Learn the core language and its features and then add tools/frameworks as needed. Lately it feels like we're teaching new devs popular frameworks and completely ignoring the fundamentals.
Yep. But business requirements dictate what happens and these frameworks are the fastest way to achieve business goals, which sucks as when the frameworks lose their appeal, those devs are gonna struggle to transfer their skills to something else.
An anecdote: I was sold a similar story on CoffeeScript back in the day, stressed myself out learning it, only to discard it a couple years later. TS won't have an identical fate as its shepherded by Microsoft, but eventually it will go the way of the dodo (whereas core JS will still be humming along).
[1] https://youtu.be/SdV9Xy0E4CM?feature=shared&t=380