There are different kinds of agnosticism. Weak agnosticism says that we don’t know but one day we might find out. Strong agnosticism says we don’t know and we will never find out.
Evolution has been proved by humans applying their rational mind to available evidence. Yet there is no reason to suppose that the human mind is equipped to make a final determination about the world in itself. We would not imagine that a chimpanzee has accurate models in its head for things such as how weather comes about or how food grows, although it probably thinks something about those everyday experiences. It probably doesn’t even have a conception that its perception is limited, even though it appears to be very limited from our perspective. Similarly we as humans don’t know what we don’t know, and we don’t know which of our perceptions and deductions about reality are not only wrong, but miss the point entirely. The only way to avoid this conclusion is to assume that humans are uniquely equipped to understand reality in its fundamentals and to explain why that should be the case. If there is a key aspect of reality that requires perceiving the world in terms of extra dimensions that we can’t perceive, or colours outside our spectrum, or echolocation which bats have and we don’t, or yet other aspects of perception that we entirely unaware of, then we may be missing something fundamental about reality which entirely changes the picture of how we came about. When you really think about it, the idea that there aspects of reality that humans don’t have access to is actually more likely than not. We can see the limitations of the creatures around us but we cannot see the limitations in ourselves because we can only perceive using our own limited perception.