your objections would apply to any constructed international language. The only alternative would be for a language to be imposed through some sort of imperialism. Even that leads to variants that border on mutual unintelligibility.
Certainly they would apply. Imperial imposition of a common language has been tried - unsuccessfully - time and time again: China, Rome, the prohibition of some Native American tongues, etc. On a much smaller scale, my grandmother's parents imposed German on her and her siblings, and yet none of the children grew up understanding the German language (beyond the baby songs and curse words.) Language cannot be imposed on a people for any length of time. The natural changes that occur within populations that are not in constant, two-way communication add up until, as you say, the disparate populations are virtually unintelligible to one another. The language variants drift apart thanks to the accrual of thousands of small changes that are not transmitted from one group of speakers to another over time.
So it doesn't really matter if the imposition is made by a tyrannical government, a group of intellectuals, or the head of a household. All are working against a human imperative: to speak in a way that serves one's
individual needs. No one language or language form will ever do that for everyone.
It's convincingly parallel to organic evolution in every way except the time scale.
