Human languages aren't just a set of more or less arbitrary conventions relating groups of sounds with meanings. Language is probably humanity's greatest and most advanced technology, making most of the other ones possible. And it's also art and play, a repository of original wisdom encoded in the various etymologies. It steers thinking down certain pathways in ways which are hard to even point to - because it would be a bit like the finger trying to point at itself. They are collectively created artifacts which encode the wisdom of generations. The deeper, wider and more diverse that pool, the more powerful the product. A human language invented by one person or by a group of people cannot ever compare in depth and richness to the languages most people use to communicate and think.