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.
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...
In other words, you're asking folks to not just learn something new, but also forget something they've perhaps invested a great deal of time and energy into already.
Sometimes, that tradeoff is worthwhile. But it's never free.