This point might be valid in general, but it can't apply to programming languages. There is no way to do language design in a committee (one might have a shot at enhancing an existing language, but it's difficult).
I'd also argue that languages on the Web should be held to a different standard than general-purpose languages, since there are five primary players and the Web as a whole will be worse off if some of the browsers refuse to implement what other browsers are pushing.