I've tried several well known (and regarded) JS Frameworks. They are great up to a point. Then I get stuck - digging into the source code, re-reading the doco etc. The corner cases brought up by my projects means writing some core JS. So I did learn a lot of neat techniques, etc. So there is value in that.<p>These days, I mostly use core JS. I find it easier to use the tested modules that work with the types of projects I happen to work on.
Are you sure you are not conflating DOM and browser idiosyncrasies with core JS. ECMA-262 is a well defined language, very much influenced by Scheme but in curly-brace (i.e. C, C++, C#, Java like) camouflage.