In my opinion - any lib in any language doesn't matter to being good developer.
But, it's great to growth your skills by using or investigating sources of that libs anyway, so just don't stop and keep learning.
For about 8-9 years of working with js and js libs, i've passed long way from things like mootools, jquery, backbone, angularjs to modern tools like angular and vue2, and every new step was a great experience in vanilla JS too.
Also, every new step in that way becomes to be more easier and faster to build complex apps, so with knowing these stuff you also becomes more productive developer.
The only thing i don't understand is framework-centric-developers, like it was 5-6 years ago with jquery - in that time there was a huge amount of people that knows only jquery and nothing else, and tried using it in any project, no matter how simple it was.
Screen from funny thread in stackoverflow about jquery
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