It seems like 90% of this can be achieved for free using a language with duck typing and named parameters. But of course we know codes written in those language

It seems like 90% of this can be achieved for free using a language with duck typing and named parameters. But of course we know codes written in those languages are often not robust and inmaintanable. What is missing? Is it the static typing? Or that all of these goals are implemented mindfully? Maybe the key is in how you document the principles.