There were many lingua francas of which French was supposedly the first global lingua franca. That changed and it became English (from what I understand). We will probably see another language become the lingua franca, so my question is: should it be English? Are there better candidates out there? Why / why not?
That may not be entirely true. Some studies have shown that Danish children generally take longer to learn to talk than children from other Scandinavian countries, which are incredibly similar in most other aspects. The leading hypothesis is the complicated phonology is to blame.
Popular science article in Danish, summing up the several studies
The researchers themselves however also make the valid point that
But I was speaking in general terms, anyway. Language, being a natural phenomenon, of course has lots of variation.