JavaScript isn't the only programming language around. I'm not the strongest around with JS either but I can figure it out as necessary -- knowing C/C++/Java/whatever means you can still grok "this looks better than that" for most cases.
If I'd asked an AI coding tool to write something up for me in Haskell, I would have no idea if it had done a good job.
Analogously I'm quite proficient at C++, and I can easily look at a small JS program and tell if it's sensible. But if you give me even a simple React app I wouldn't be able to understand it without a lot of effort (I've had this experience...)
I agree with your broad point: C/C++/Java are certainly much more complex than JS and I would expect someone expert in them to have a much easier time picking up JS than the reverse. But given very high overlap in syntax between the four I think anyone who's proficient in one can grok the basics of the others.