its proverbial lack of precision...
I don't believe you could be more wrong
about the main bodies of Englishes (note the plural) used in the modern world, whether US or UK or Antipodean or other variants. The language has evolved over a long period of time by adopting loan words and new transfusions of structure and meaning from many, many other languages, with the result that it has the largest core vocabulary of any major world language. The effect of this is to allow unprecedented control over nuances of meaning between almost-synonyms drawn from different cultural roots.
As for any grand plan to conquer the world - nah! The current state of English as the de facto
world language is largely a historical accident of two major world empires having used the same core language. Other peoples now adopt it out of choice to enable their personal needs and dreams.
Esperanto, like so many bureaucratic grand schemes, will always fail when tested against this popular will enacted out by millions of individuals taking their own personal choices. There may well come a time when English no longer has such a key role to play; but we can be certain that it will NEVER cede authority to an artificial construct of this kind!
Now Chinese might be a more interesting possibility...