good point, but a sunk cost. New programmers, such as young* developers learning front-end architectures for the first time, never learned all of the underlying platform. So they can spend the next ten hours achieving x amount of progress in pure javascript, or y amount of progress coding atop a framework.
As an analogy, the difference between x and y is why, in decades past, so many inexperienced programmers started coding C without ever learning assembly - and then later, so many people started codig in a high-level interpreted language without ever learning C/C++. (Which may have been the language the interpreter was coded in, or even available directy if they needed it, such as in very performance-oriented code.)
* a general observation, more rigorously read: inexperienced.
That only works if the framework actually does work as a complete platform, though - that is, if you can get away with forgetting (or never learning) the underlying platform once. To go back to Angular, it would mean forgetting all about the non-Angular-friendly parts of the DOM, events, etc. and never needing to use them again.
I haven't written any assembly in many years now, but for a good while it was still pretty important to maintain that knowledge - you never knew when you'd need to use it for a routine here or there that was just too slow or cumbersome in C. And still, long, long after that, debugging C required at least some assembly knowledge if you wanted to get home in time for supper.
And this is where I see folks getting into the weeds with stuff like Angular: if you completely forget (or never learn) the underlying platform, it's entirely too easy to get stuck when it comes to debugging or even performance issues: you know it shouldn't take 3 seconds to render the page, but if you can't look under the abstraction then you're hosed.
So eventually, you're stuck learning the whole stack anyway. And now it's not a sunk cost: you have to forget what lies beneath every time you sit down...
As an analogy, the difference between x and y is why, in decades past, so many inexperienced programmers started coding C without ever learning assembly - and then later, so many people started codig in a high-level interpreted language without ever learning C/C++. (Which may have been the language the interpreter was coded in, or even available directy if they needed it, such as in very performance-oriented code.)
* a general observation, more rigorously read: inexperienced.