It's not about that. Even if I liked COBOL, I wouldn't want a world where only COBOL can be used. And it doesn't make sense that this world has to be artificially enforced when there is demand for variety.
Not sure what you mean by the "same basic semantics". I think the semantics of Go and Elm are quite far away from JavaScript. Dart less so, but it's enough to change the developer experience quite a bit.
I don't particularly like x86 instructions, but they also don't bother me that often.
Granted that JavaScript isn't sufficiently hidden yet, particularly in debuggers. That will take a few years. On the other hand, it's significantly more readable than assembly and getting better, so as a compiler target language, I think it will work out okay.
The forces here are no more artificial than the ones that made the industry standardize on x86 and (later) ARM. Popular, accepted standards become more popular when the barriers to alternatives are very high, as can be shown by the people who tried and failed with strong alternatives.
It's not about that. Even if I liked COBOL, I wouldn't want a world where only COBOL can be used. And it doesn't make sense that this world has to be artificially enforced when there is demand for variety.