With a concurrency-safe garbage collector (which isn't even hard to come by) I would argue the exact same is true of JavaScript. It really isn't a language detail and I would argue it would be a weekend project to get real multithreading working for JavaScript (as in, to the point where it works as well as in C, which is to say it might require tons of mutex locks everywhere).
It can be done, and has been in Rhino, Nashorn, and graal.js. The problem isn't in the language per se but in the libraries provided as standard (mutexes, thread safe hashes/property access etc.) and in the implementation. It's much easier to build a JIT when you don't have to worry about concurrent threads of execution, and converting a single threaded JIT to a robust multithreaded one can take a lot of work.
