Only an Atheist has any chance of developing any level of true understanding of Nature, The World/Universe, and the Human Condition.
This is because a Theist's mind is polluted and hobbled, and cannot think clearly. Theism metaphorically poisons and disables the mind's ability to connect cause and effect, and thereby sabotages the brain's ability to build accurate mental models of how the world works, and how humans behave.
But if you are free from the destructive influence of religion on your mental faculties and your ability to reason, then you can see the world and the human being for what they truly are. Of course, the actual amount that you understand those two things will depend on how much, how broadly, how deeply and how intensely you have studied them. But at least you have a fighting chance of making decent progress towards a hefty amount of understanding, without religion's blindfold.
One thing about the human condition that empowers a person's ability to understand themselves, to understand other humans, and to understand the world that humans build (and the cages that they choose to live in) is to realise with clarity that the world that we perceive is not the real world at all. What we think that we perceive as reality is fact nothing more than a simulation of reality that we construct inside our brains. So, in that sense, the crackpot pseudo-theory that is currently wasting some people's time: that the Universe is a complex "simulation" of reality being created in some kind of computer, is not complete nonsense. In actual fact, these people's ideas are closer to the truth than they know - the Universe is indeed a simulation - one that each person continually creates for themselves inside their own brain, and simultaneously lives within. So where the crackpots are wrong is that there is not one vast, grand simulation that we all inhabit, rather, there are billions of simulations of the Universe running. There is exactly one simulation of the Universe in each person's head.
Starting from that premise - that you are never perceiving reality, in fact you are only ever perceiving a copy of reality that you are creating (in real time!), now you can uncover some real revelations:
We don't actually perceive reality very clearly at all. Our brains are very limited in their ability to sense and receive data, process it, and decide how to act on it. In fact our brains are quite poor at doing all of those things, nevertheless somehow we muddle along, and we constantly create art, mathematics, science, invention, politics and war.
One particular power/ability that the brain has, which most people never give a thought to and never realise that they have - is that we can choose what we want to perceive. We usually call it Imagination, but that's a limited description of what our brain is doing unconsciously all the time, and it's a limited portrayal of what our brain can do at our command, under our will.
We can choose what to perceive at any moment. We can allow our senses to receive input data, but instead of letting it pass straight through the brain to be acted upon, we can morph/change/distort/twist/alter/censor/block any particular input data ... if we use our imagination pro-actively, with enough sheer force of mental will. Actually it doesn't really even require any effort, because all people are doing this all day every day - we all twist, distort, filter, selectively ignore some of our sensory perception at all times. Imagine this scene: you and someone else are facing a closed door, side-by-side. The door opens, and you both see what is on the other side of the doorway. Each of you will perceive something different. Not merely because of your difference viewpoint perspectives, but because of what you think about the thing that you can now see. Neither of you will perceive the thing clearly. Each of you is (partly) the sum of your separate experiences - and what you perceive on the other side of the doorway will be coloured/filtered/tainted/distorted by your own personal memories and experiences. Therefore, both of you will perceive wrongly.
The immense power of the human imagination is that you can choose how to perceive, if you want. You are in control of how you filter/distort the scene before you, how you want to experience the world.
Why would you want to do that? Because your subconscious mind literally cannot distinguish between reality and that which is vividly imagined. If you vividly imagine a scene, your autonomic nervous system will respond as though you are actually experiencing that scene. Your heart rate, breathing, skin temperature, blood pressure, etc. all change, because your body has no choice but to obey the mind's imagination. If I ask you to slow your heart rate, your heart rate will not change, but if you vividly imagine yourself relaxing on a beach, you can change your heart rate.
Why is learning this skill important? Because most people have got this faculty running rampant and out of control inside their minds. Eg. if they are stuck in a boring conversation, they are imagining being elsewhere, so they are not mentally "present" - they are not paying attention - they are not absorbing the sensory input from the world around them. At that moment, they are living in a fantasy land inside their own minds.
Religions, cults, revolutionaries and politicians take advantage of this - and they use manipulation techniques to get people to hold in their minds a contrived, constructed pseudo-reality, so that the flock of fervent, brainwashed, abused victims all choose to see the world through a shared lens that distorts what they see into a similar, shared mass-hypnotised vision. If a mix of people looked up at a cloud in the sky - all the Christians might see a Winged Angel, while all the Moslems looking at the same cloud might see Muhammad on a Winged Horse. Their brains would do this automatically, because their brains have been trained to keep those types of images in their mind's eye at all times.
Well, who cares? What's the point of all of this? Why does this even matter? Of course we see things the way were taught to perceive the world - our families, our teachers, our governments, our (cough, cough) religions, ... they weren't evil or stupid, so what they taught us was for our own good. ( ... wasn't it?)
No. The human compulsive behaviour of imprinting your beliefs onto your children's minds is not helping your children. It is severely harming and damaging them. Not just religious indoctrination - also your political leanings, your business notions, your racist attitudes, your idea of what a family should look like - all of those things shut down and excise vast oceans of freedom from your child's mind and from your childrens' futures.
Why do people feel compelled to share their beliefs with others? With their children, with strangers, etc.? Why do religions want to spread - throughout the neighborhood, throughout the country, across the globe?
Trying to believe something that you were told to believe is not the same as living in a fantasy world that you created in your own mind.
The problem with religions, cults, business and politicians is that they utterly rely upon you staying in their fantasy land. They utterly need for you to keep the visions in your mind, the visions that control your behaviour. They utterly need you to keep showing up and to keep giving them money and power. They keep you under control by endlessly repeating the commands and the stories that keep you maintaining the visions in your mind. Call it brainwashing, propaganda, advertising, mass/ministry, etc., it's all about re-telling you the stories so that you keep re-painting the same pictures in your mind, so that you keep perceiving the world the way they want you to, so that they feel safe in numbers. They always want an adoring fan-club because their beliefs can't possibly be wrong if many other people believe them too! The Leaders of cults, political parties, etc. all share a common Cause: - which is always only to spread their beliefs further and wider. And if you and your family are willing to sacrifice your lives for the Leader's cause, then that's even better, because it strengthens the Leader's claims that the beliefs must be "right".
The way to save yourself from others having this type of power over you is: don't believe anything. Don't try to force your will upon the world - you cannot force the world to be exactly compatible with your perception filters. Stop choosing to perceive what you want your eyes to see, what you want your ears to hear. Instead, just let the "virtual reality" in your mind reproduce an exact copy of the world around you. Let your mind be like a mirror to the world in real time. Just pay attention to your senses and let that sensory input information captivate your imagination. Lose yourself in the world - just relax your mind's constant struggle and don't try to make your imagination over-power what your senses are perceiving. Stop mentally fighting the world and just let it in.
In that state of mind, something becomes very obvious: the world has no meaning. The world has no purpose. You don't have to strive to become something. You don't have to use the power of your imagination to change the world. You can just be.
And then something else becomes obvious too, something even cooler - if you do want to change the world, your imagination is where you need to start. Even if you don't want to change the whole world - if you just want to change something about your little piece of the world - your imagination is the necessary (but not sufficient) key to unlock your potential.
Do you see now, how Theism disempowers this natural ability that all humans innately have? You cannot tap into this mental ability and make use of this mental power, if religion has surgically removed your innate powers of imagination to control your reality.