I think the point is not if something is out of reach of a basic human, but more that if it takes 10 years to reach basic proficiency, then it's not a language

I think the point is not if something is out of reach of a basic human, but more that if it takes 10 years to reach basic proficiency, then it's not a language that will be fit to share with a huge amount of people from different backgrounds. Now, I personaly think that if French actually reached a point where it would be shared as common language by billions of people it would have been broken down to a more efficient form. Creoles and other dialects derived from french all seem to get rid of the redundant bits.