Ok, so, just about every language that humans have ever spoken was not 'created' or 'planned'. There are such things as constructed languages (and among their number are such languages as Esperanto, as well as Quenya and Sindarin from Lord of the Rings, Klingon from Star Trek, and Na'vi from Avatar). But languages like French and Japanese were never constructed in the same sense. Linguists call them 'natural languages' because they developed without any substantial top-down planning. People who speak modern French have a linguistic continuity stretching back to the time of Caesar and several thousand years earlier than that. Modern French doesn't look too much like Latin, of course, but the differences between the two are the product of a complex process of incremental change.

This isn't to say that no human intentionality has ever had a hand in shaping modern language, but that intentionality has never really been systematic nor dictatorial. To put this a bit more simply, while it's true that any person can coin a word (or use a certain construction or pronunciation or whatever), it takes other people to make sure that the innovation survives. So, while it's true that people do consciously use certain innovations, and these innovations can take hold and choke out older forms, we shouldn't understand this as people 'creating a language'. Rather, they're incrementally modifying something that has been around for several thousand years.