I think I just came up with the perfect example of the principle "evolution often settles for just good enough"

Why is it so difficult for most people to learn languages, even though our brains have evolved to use language, and in fact now require it in order to function socially? Because, since it takes so relatively long for humans to mature(enough time to relatively easily pick up a language gradually), and since, for most of the history of language, it has only been necessary to know one language to get by in any particular community, there hasn't been enough of an evolutionary incentive for it to become easy for any given individual to be able to learn multiple languages.