> Thats what makes it a new language. C is just sugar on top of assembly.

I think that's a bad example. C isn't a sugar for assembly: For example what assembly code does a function prototype desugar into? Sugars have 1:1 mappings with host code

Maybe you're just being rhetorical about the spectrum of macros, sugars, and languages, though.

(In my opinion, a better target for that criticism, in JS land, is the Jest test framework, because of all the reordering magic it does that break fundamental ES semantics)

> Why className instead of class?

This hasn't been a constraint since... I want to say React 18, six or seven years ago? I might be misremembering the history but I think that was only a problem in the Early Days when there was paranoia about whether JSX needed to be conservative with reserved keywords