1. Not every question has an answer we can comprehend (see quantum physics). Some answers might be comprehendable but the information we'd need to answer the question is inaccessible (like "what was the population of a given lat/long coordinate in the year 1345?")

2. Why do I need to answer that question in order to answer other questions? Assuming some priors and is always a necessary limitation. If you learn new stuff about those assumptions or find new information that indicates the priors are imperfect (as they likely are) you update a bit.

"The best you can do" is a fundamental aspect of world.