It’s useless knowledge for most people now. Like knowing assembly.
I currently work with devs who've done things like create a Map and then assign properties directly instead of using .set and .get.. I'd say that shows a pretty significant lack of fundamentals
People just assume every data structure operates like an array since it is the most commonly used without realizing the underlying object nature of the language. Like the idea of getters and setters coming from OOP paradigm is lost to fresh devs over the last 5 years using the FP paradigm as their primary means of coding in React.
So yeah some of the fundamental are missing but also most of the time this knowledge probably isn't utilized by React FP only devs in their day to day.
I've interviewed a few people who don't know how some of the array methods work, and those are one of the most important parts of knowing how to write Javascript.
https://lolware.net/blog/react-xss-protection-cheat-sheet/
The feedback I got across the board was generally "what even is this code? If you it to work with react why isn't it a hook?"
I mean, it's correct that people who ask such questions should spend a year doing web dev without React probably (and maybe learn basic programming concepts). But the people who comment to you about that post seem to be self-selected for not knowing much about JS.
People who know their ropes aren't left with any questions by your article :) and probably know about everything it contains already.
Still, feedback from me: good content, especially for beginners!