Learning a language as an adult is completely different from learning as a kid. Your hypothetical “dumbest French person” would not have been able to learn Fren

Learning a language as an adult is completely different from learning as a kid. Your hypothetical “dumbest French person” would not have been able to learn French as an adult, the same way that the most physically fit 100 year old could not survive the falls down the stairs that 3 year olds do without even crying.