> How did it happen that junior JavaScript developers feel so insecure about using the standard stuff?

I know a lot of "developers" that are learning frameworks and not javascript. When you start in a black box then you look for other black boxes to fill in the gaps you need.

I am not even opposed to that. I strongly believe in never re-inventing (unless its academic) what can be used and has been tested, but when the developers are not javascript developers but react, vue, angular developers. Then you get this gap where the inexperienced are afraid to outside of what others have built.