Isn't the real problem that Ruby's "magic" a lot of the time relies on monkey-patching stuff?

I mean, Javascript's modules also are dynamically executed and then returned as a singleton module object (also cached, so only the first require actually runs the code before the module export). This means you can make a module which requires other modules and monkey patches methods inside them (this is how mocking actually works), wrecking havoc amongst all other dependencies, but library authors just don't.