Another issue is that if look through job postings carefully, you will see the pattern there where framework knoweledge is valued above everything else. It is "React Frontend Developer" or "Vue Frontend Developer", not just "Frontend developer who is capable to pickup whatever technology we use".
There are reasons for that, of course, but it is hard not to see that this approach will likely skew hiring into looking for a specific knowledge in candidates. And candidates are going along with a path of the least resistance and learning stuff they need to work with backwards.