Non recursive language does not allow you to give commands more complicated than "you do this", for instance saying "tell X to do this thing at this time in this location" is impossible without recursion. You might be able to get as far as "tell x to do this" since you are essentially just saying "repeat these words to X" but you have no way of providing context such as the time or circumstances when X should be told or when X should be told to perform the action. All organization and command would have to be done spur of the moment. There would be no possibility of planning in advance or communicating abstract concepts and thoughts to others.

Even a small group of people with this ability facing another group without it would have an overwhelming advantage, they could deceive, plot revenge, strategize, distract, and confound their opponents with their seemingly magical ability to know what members of their own group were to do and say before they did it. They could conceptualize solutions to problems that the others could not even begin to imagine. They could invent new objects in their mind and then execute those plans or tell others about them. They could create new words and concepts in language through combination and juxtaposition. They would quite literally be super-human, every one of them a Napoleon and an Einstein and a Da Vinci and a Shakespeare at once.