The computer is a machine. It understands one language. Everything else is sugar on top. The language you should choose is the one that exists at the right level of abstraction for the problem you're trying to solve. That's a very academic way of saying, "choose the right tool for the job."
Personally I'm of the opinion that you can get really far knowing C and Common Lisp. They represent two fundamentally different models of computation and all of the other languages (save the Smalltalk offshoots and obscure ones I haven't had the pleasure of experimenting with yet) are essentially sub-sets of functionality from one or both of these two languages.
It's too easy to get caught up in the "feature creep," of all of the languages available today. Some will claim "immutability by default," is a feature. It's not. Any sufficiently sophisticated evaluator of a language can stratify a program into a process capable of emulating a machine that can treat all memory as "immutable by default." It's important to remember that often these languages are created to solve a specific problem and then evolve over time to become more general. It is best, in my experience, to just go straight to the source and work down to what you need.