Why have we accepted that we "can't know everything"?

Hey everyone, I’ve been thinking about the limits of medical knowledge.

If you compare an average med student today to a doctor from 300 years ago, we are basically "miracles" to them. We know more about a single cell than they knew about the whole body. This proves that the "threshold" for what one person can know has shifted massively over time.

So, why do we constantly tell ourselves that it’s "impossible" to grasp every specialty deeply? Who sets that limit? Some class toppers give you some hope that this could be possible who seem to have a total grasp of everything, answering every niche question,

I know maybe I don’t have the right to adhere that question because I am the type of student who struggles with barely knowing the “General” I mean what every family doctor should know .

But Is it actually impossible to be a master of everything, or is that just a limit we’ve collectively agreed on because it’s hard? I want to know the why behind every diagnosis, not just the "high-yield" facts for an exam. Am I being too ambitious, or are we just underestimating what a modern doctor can actually achieve?