There are three claims that Chomsky makes about the existence of Language Acquisition Device (LAD).
The first claim is that children can understand all kinds of sentences without having to have heard or learn them before. To this we can say the same thing about adults as well. In fact, every time I open a book (or any other piece of new writing) I haven’t read before I am comprehending it as well. This act is so common and normal that we should be thinking so much about as being something special.
The second claim is that all language seems to have universal elements. To this, one can also argue that it is not the elements of language that is universal but the rather it is the shared reality that is universal.
The third claim is that some grammatical principles are acquired regardless of culture or intelligence. To this, I will argue in a similar to the second claim that the medium of language is universal so that any language only have a limited number of possible choices available to it. Furthermore, for what purpose or reason would their be a develop of a language away from general principles. If such a principle does exist surely it would have been developed and supersede the other languages as being inadequate.
While we probably do have more of a capacity for language it is probably more generalised than Chomsky would like to believe.