I've never thought of ES5 as simple, consistent, and easy to read. There are plenty of features that many devs wouldn't recognize (ie, "the bad parts"). They've fallen out of vogue because there are better ways to do things, but they're still part of the language. I, too, would love a simplification of the language, but as you mention, backwards compat is necessary.

And what does `case` not do that you want it to? Fall-through? Re: forced destructuring, if you want to switch on a value, why not just wrap it in an object, eg, `case({ someVal })`? It's not perfect, but I'd prefer consistently using `case` to the confusion you call out re: `case` vs `switch`.