Two statements on simplicity and IALs:
1. "The best international language is that which is easiest for the greatest number of people." Otto Jespersen.
2. “English is far too difficult to be an appropriate IAL.”;
I strongly disagree with Jespersen’s dictum, but fully agree with the second statement.
The value of a language is based on the uses to which it can be put. My dictum would be:
"The best IAL is that which is most useful for the greatest number of people, worldwide."
People learn languages because they are useful, not just because of their simplicity.
As difficult as it was, Volapuk showed that such an IAL could be somewhat useable.
People who adhere to Esperanto tend to find its circle of samideanos to be useful.
They put up with its long identified difficulties because of such things.
Ido was designed to be easier, and was. But it did not supersede its forerunner.
IALs like Frater, Glosa, etc. were perhaps simpler yet—Toki Pona is far simpler.
But the push for greater simplicity can disrupt usability in certain domains.
The global language should be the most useful for all persons and purposes.
This means world literature, commerce, science, law and diplomacy, the internet, etc.
Right now, English seems to be fulfilling that purpose . . . to a degree.
But it remains needlessly difficult, takes almost a lifetime to learn well.
English is also tending to split into regional variants.
(Consider its complex and varied vowel patterns!)
English is IMO inappropriate as the long-term IAL.
I have great respect for Jespersen, but I believe his famous dictum must be discarded.
An IAL can be complex in certain ways, if that complexity adds enough to its usability.
Much of the complexity of English detracts from its usability.
Best regards LEO