This is really only a question which can be applied to those learning a second (or more) language, it seems to me. It would be virtually impossible to teach a native language as a system, as the first words and sounds spoken by babies are to communicate. We all learn that words have the power to move and persuade and explain very early on, and I see no way that will ever change. Learning another language, though, may well benefit from a more systemic approach; however, learning that language, too, is probably motivated by the need to communicate more than simply learning for learning's sake. If one simply has an academic interest in learning a language, learning it as a system would clearly be the most effective method. For everyone else, learning a language is motivated by the need or desire to communicate.