This is what gradual typing (such as TypeScript, or the use of Python annotations for type-checking) accomplishes. The issue is that it basically always is bolted on after the fact. I have faith that we aren't at the end of PL history, and won't be surprised if the next generation of languages integrate gradual typing more thoughtfully.
The problem with these two languages is that the runtime type system is completely different (and much weaker) than the compile time one; so that the only way to be safe is to statically type the whole program.
CL has a pretty anemic type system, but at least it does gradual without having to resort to this.
JavaScript caught on because it was the best casual language. They've been trying to weigh it down ever since with their endless workgroup functionality and build processes. If we get a next generation casual language, it'll have to come from some individual who wants it to happen.
No, JavaScript caught on because at the time it was the only game in town for writing web front-ends, and then people wanted it to run on the server side so that they could share code and training between front end and back end.
It's not enough to just be first. It would have been replaced by now if it wasn't fit for purpose. Otherwise we might as well not bother to critique anything.
