The nationalistic policies around WW1 and after put a stop to it.
I think it's a tremendous shame... it would be so nice to communicate with everyone in a simple language.
Note that such a language would not actually need to be actively spoken in normal live much. It just needs to be simple enough to be learn in a short amount of time and to have international backing so it is taught in schools.
Almost by definition - if a language isn't "spoken much" - it isn't really language. But rather a collection of rules and definitions.
"If a language is (or never has been) spoken much..."
it is easier to learn, even for non-europeans.
it is nationally (edit: i used the wrong term 'politically' before) and culturally neutral.
english wasn't always the most used language for international communication. until a century ago, that was french.
english replaced french because of the success of british colonialism.
there is no reason why some day esperanto could not take its place.
it is for example conceivable that people could use esperanto as a communication language with foreigners to avoid english domination out of a conservative isolationist motivation.
i edited my post to clarify.
by comparison, the speakers of latin are all dead. so, while latin has a rich historic culture, it is not dominated by any living culture.
likewise, esperanto is not dominated by any living culture because its speakers come from all over the world.
That is a very good idea. But in order to be successful such a language needs to be spoken by a large share of people internationally. The best language we have for this is English. It's not perfect, because in large parts of the world, particularly in Asia, many people don't speak it. But it's far better suited than Esperanto in almost every imaginable way.