Javascript, like python, was "simple yet flexible". Thats what made them successful.
When a language is successful, people start to bolt on extra bits of syntax and features (async, prototypes/classes, lambdas, etc). Eventually it is no longer simple, and the learning curve gets steeper for new users.
Someone comes up with a new simple yet flexible language, all the new users start with that instead, and the cycle repeats.
BASIC/visual basic/VB.net went through that cycle in the 90's. C then C++ went through that in the 2010's. Python/Javascript is going through that now. Go is about to go through the same.
