No, I do not see

Infantilism and Naivety

Do you not see a connection between your definition of infantilism and naivety?
The terms are not synonymous, of course, but the meaning is very close.
If you do not take the extremes - children who have to, literally, survive from an early age, then it is obvious that the child's perception of the world is much more naive than the adult, that is. It is infantile.
tt d.

Infantility implies that you are not responsible for your actions for everything else. If it were the same one would have been the same term, but they are two and they are different. Get to know them in more detail and do not carry them apart.