For me, all roads lead back to my beloved Heidegger. And, I think he was quite right to question the Cartesian claim that there is such a thing as a dis-embodied thinking self (cogito) autonmous from time and world. Heidegger rejected this understanding of personal identity and argued that indeed, our human condition cannot be grasped outside of our everyday projects and situatedness. Everything we know is dependent on our environment (umwelt) and is a necessary reflection of these temporal and cultural limits.
But then how to explain those people who do, in fact, get outside their worldview--outside the culture or the "clearing" into which they are thrown? I would suggest that Heidegger doesn't explain this at all. Maybe he would claim it is not possible to truly be between worlds--and yet, I believe that is precisely what happens and people can indeed take on and negotiate between multiple worlds. This is not to say that anyone can ever get beyond their everyday world into a kind of abstract objective understanding but rather that they will have to deal with multiple cultural projects and mindsets.There's a clearing, where ontology happens. It's always your clearing. There isn't a clearing for your familiar environment, and another clearing for your less common cultural environment. A cogito can't decide to switch between clearings. I would say a person's assimilation into a culture is a matter of how well different cultural environs fit in their clearing.