Nearly every religion posits some sort of hidden, immaterial realm which exists behind the visible, physical, and material realm in which we live. Often we are supposed to be partaking in this immaterial realm because who we "really" are is defined by an immaterial, immortal soul. This immaterial realm is also treated as being higher and more important than the material one because it's the realm in which gods live and which we are destined to inhabit after our physical bodies die.
However important these beliefs may be to religious theists, there isn't any solid, verifiable evidence that even suggests any of it is true. On the contrary, everything we do know and everything we continue learn points to the conclusion that all of those claims are completely false, and instead that the following are true: life is material and natural, we don't have anything like an immaterial or immoral soul, and an immaterial, disembodied "mind" like gods are supposed to have just isn't possible. When all available evidence points away from a particular position, that doesn't necessarily mean that it's false, but it is unreasonable to believe it.
The evidence against the claim that our minds are really immaterial and not a product of our physical brains is unequivocal. When a person's brain is stimulated, through physical implements, drugs, or magnetic fields, and put in a particular physical state, then a person's mental experience corresponds to what we know about that state. Approaching from the other direction, self-reports about particular mental experiences correspond to evidence about their brains' particular physical states. There is no reason for this to be true if our minds and mental experiences are independent of our brains; people who continue to insist otherwise offer no means for testing and verifying that claim.
All of this is true to a much more extreme degree when the brain is injured through physical trauma or certain drugs. Some destroy enough of the brain to end all mental experiences entirely. Some only go far enough to destroy or at least greatly degrade particular mental experiences — like language use or particular emotions. Moreover, injuries in particular areas lead to particular changes in mental ability — injury to one portion of the brain will affect language while another won't. There is no reason for any of this to happen if our minds and mental states are independent of our brains. If an immaterial mind is what does our thinking for us, then changing the brain shouldn't produce any, or at least any significant, changes in our thinking.
All of this is also true of other animals. It's not just humans whose mental states can be mapped to particular brain states, whether through deliberate manipulation or injury. Not only is the same true in other animals, but there is a high degree of consistency when it comes to which areas of the brain correspond to what sorts of mental abilities and mental states.
Furthermore, every species studied demonstrates increasing mental abilities as they grow older and their brains grow more complex, developing more neurons and more connections between neurons. If our mental capacity and mental states are immaterial and independent of the brain, there's no reason for any of this to be true. Moreover, people who believe in immaterial minds don't normally attribute this to non-human animals, yet they cannot explain how physical brains can produce mental capacity and mental states in other animals but not in humans.
All medical and scientific evidence we have points to our minds, our memories, and our personalities being products of our physical brains. This is no less natural and no less material than how our physical bodies produce other processes, like digestion. If this is true, it means that when our physical brains die then our minds, memories, and personalities will also die. Since these are what make up who "we" really are, then the death of our physical brains means the death of us as well — if there is any sort of immaterial soul, it's not "us." It doesn't do our thinking, it doesn’t hold our memories, and it doesn't express our personalities. This makes the existence of immaterial minds or souls irrelevant at best.
These issues also impact notions about the existence of gods with disembodied minds. Since everything we know about minds, thinking, memories, and personalities requires the existence of a physical brain as a basis, it's difficult to credit the idea that a disembodied mind without a brain is even possible. Religious theists have certainly not offered any explanation for how this would even be theoretically possible, much less provide evidence for it being an actual state of affairs. It is unlikely that such a disembodied mind exists and, therefore, that a god exists.
None of this is unequivocal proof that no gods can or do exist, nor does it prove that no religions are or can be true. It does, however, provide a strong basis for doubting that some of the most fundamental claims about gods and religions are true. Although they are not logically excluded from being true, they are excluded from being very likely true. This amount of contrary evidence makes belief unreasonable.
There is nothing more frightful than ignorance in action.