>Languages are substantially different. You don't (and can't) understand every concept under the hood to drive the thing. You can't add and substract features, they're interdependent.
All the above are patently false.
-- Most languages in common use are NOT substantially different. Not just obvious things like Java/C#, or F#/Haskell/Ocaml/ML but even C# to Ruby or Objective-C to Javascript are not that different, much less fundamentally.
-- For most languages a lot of good programmers can and DO understand "every concept under the hood" (VM internals, runtime costs, etc).
-- And you sure CAN (and language designers do all the time) add and substract features. They add features from other languages and they remove some to create theirs. And then, when the reach version 2.0 of the language, they cherry pick and add some more features from other languages, or remove out-of-favor features.
All the above are patently false.
-- Most languages in common use are NOT substantially different. Not just obvious things like Java/C#, or F#/Haskell/Ocaml/ML but even C# to Ruby or Objective-C to Javascript are not that different, much less fundamentally.
-- For most languages a lot of good programmers can and DO understand "every concept under the hood" (VM internals, runtime costs, etc).
-- And you sure CAN (and language designers do all the time) add and substract features. They add features from other languages and they remove some to create theirs. And then, when the reach version 2.0 of the language, they cherry pick and add some more features from other languages, or remove out-of-favor features.