Would you hold another programming language, such as JS, to the same standard?

Of course. I think JS is full of mistakes. To be fair some of the more egregious ones have been fixed, but there are still plenty left.

I'm a big believer in learning new stuff, when that stuff has lasting value. However it is far more efficient to fix things, a one time cost that benefits everyone, than to ask everyone to learn the quirks of a tool, a cost that is paid every time someone new comes along.

Are you implying that having both String.prototype.substring and String.prototype.substr is somehow confusing?

JS is in general better because by the time it came out people knew what to expect from a scripting language.

CSS didn't really have a lot of earlier styling and layout languages to copy. Also the original vision was much more limited.