Um, no.
When it comes to animals, you may take the view that they naturally develop their innate skills to their full potential, although it would make some sense to have them start at some level and then develop their skill with age. Thus, the current situation might be considered to use a simplified simulation.
It does not, however, make sense to say that Leatherworker Urist, who's made High Boots his whole life, makes a career change to a poet, visits your fortress, and becomes a citizen, at which point he no longer knows how to make High Boots (which is the entity based situation we have now).
Intelligence should be a property of the creature/race, while entities may provide skills they can acquire within that civ (it's really over simplified that you send 7 noobs to set up a site but these noobs somehow know how to make workshops that know how to produce things, but it's probably a required simplification for isolation fortresses to work). In further development DF ought to allow sites and civs to learn new tricks (not only magic ones), such as e.g. how to make things they didn't have the knowledge for previously, e.g. from citizens recruited from other civs (in fact, there is already such a potential, but it's currently limited to arts: poems, music, and dances can be learned from visitors, and this knowledge is in fact individual, not site/civ based).
Slow Learners, meanwhile, might well lack the intelligence to understand some of the more complex tasks, and thus fail to learn "advanced" crafts, and may well be limited in the extent to which they can learn simpler ones.