I know you are joking but based on my purely anecdotal personal experience, the French (at least in Paris) can now speak and are willing to speak in English much more than a few decades back.
The first time I went to France, almost 25 years back, I had a rough time communicating at restaurants or even buying tickets at the Paris metro stations. Not sure if the latter was an ability or willingness issue because even holding up two fingers and saying "two tickets" was apparently indecipherable. Had to muster my school days French and say "deux billets" to produce instant results.
Edit: And no, the two fingers I was holding up were not the middle finger of each hand :P
well because it's kind of a forced adoption in an ideal world we would have developed a common tongue by slowly merging the languages, or at least would have taken one that's pretty good and then improve on it. For example Hungarian is much better in the sense that what you write is what you pronounce, not the mess that is English, so in an ideal common tongue I feel like that aspect would be adopted.
Of course Hungarian also has stupid parts, ly (<- that's supposed to be indeed one letter) and j is the same thing. x is just ks, y is pronounced the same as i and w is just v so there is some extra fat on it, but other than that the 44 letters cover all the sounds you make while pronouncing words.
Hungarian is like Chinese to most romanic / germanic languages.
While being excellent in describing every little thing pretty efficiently and short, the problem I see with highly advanced languages is imho that they are pretty complicated to learn.