But obviously, that skips over how language and cultural and religious differences act as catalysts to conflict. So anyone wanting to explore those themes would be better off writing about the world BEFORE such a contrived language just wills into existence...

For my world, once magical long-distance communication develops, the need for a "common" language built up. So the regions with most language diversity started mushing them all together and came up with 'Gaian'. Basically, if we invented English for the world rather than forced it on everyone.