You are oversimplifying the means with which we interact with reality. First, we know our perception is based predominantly on our interpretation of past experiences, which is why, we employ less restricted techniques towards discovery of the unknown. This is where conception comes in. The idea that our planet is a sphere/spherical was conceived millenia before the telescope was invented. The idea of the atom is also an approximation of what energy would be like in those circumstances. We are yet to observe actual atoms. Reason does not just employ logic to give context to past experiences, it also tries to project possibilities, and the success so far is because of the underlying fundamental unity of fact/reality which we all presume and are yet to be proved wrong.
It is unfair to suggest that humans don't have the capacity to know everything when we have a limitless potential to unfold. We are like children, we are constantly growing and learning. The coherency to the idea of a greater intelligence/system of activity which exists even in fields like metaphysics shows the degree to which we can conceive of fact/reality. Even though astrology is not dependable in the sense of constellations and the impact of celestial bodies on our behaviours, can you imagine how much information those primitive civilisations conceived of and the degree of proximity to the principles which they are based on. It is quite baffling that they would conceive of constellations (collection of celestial bodies), only for us, with the use of equipments for actual observation, to discover solar systems and galaxies. How ingenious is it for them to conceive of psychology based on a relationship of the external world and our instinctive behaviours. They may have put too much significance in the abstract but, considering how sound the idea of attitude and response to external stimuli is, all they needed was the right perspective and modern science would still be ancient metaphysics.
The limitation of perception to the bounds of experience is a significant one because it compels us to focus our efforts towards our immediate circumstances before we think to venture further. What good is there in knowing everything when we do not have comprehensive control of our persons, impulses, thoughts (biological, psychological, social, etc). Charity begins at home is based on a universal principle: you cannot see in others what you do not see in oneself. We cannot carry out conception without the development of perception, and the greater our perceptive abilities the further we can conceive.
"Imagination is more important than knowledge. For knowledge is limited, whereas imagination embraces the entire world, stimulating progress, giving birth to evolution." - Attributed to Albert Einstein.
However, without requisite knowledge our imaginings would yield little of significance.
As to the computer analogy, I think it is flawed just as the brain-in-a-vat hypothesis because they imply a separation between fact/reality and our perception of it. What we perceive is an expression of fact/reality not something disconnected or veiled from it. Someone said, "a logician could infer the niagara or the pacific ocean from a drop of water," the same applies to observing a computer screen or from the perception of an expression of fact/reality. If it hadn't happened, we would not be having these kind of discussions.