Yes, I remember encountering Esperanto many, many years ago. I do not know how much it has spread or at what rate, although your comment seems to indicate that there has been at least some progress. (Hope I didn't misunderstand you.)

English does serve well as a lingua franca. It has also become a pluri-centric language. Who knows, in the future its development may mimic that of Latin, which eventually spawned a number of related but distinct languages. Right now, it's the best we've got. Two huge English-speaking empires have given it a vast distribution.

And with regard to native speakers: sure, there can be no doubt that they have an advantage--which may be a greater consideration, say, when producing a novel than when reading one. But your point still stands.