Existentialism says you are in a cold indifferent universe full stop. It says another reason nothing is about you and nothing is giving you meaning is how you are literally nothing in this incomprehensibly vast universe.
H. P. Lovecraft spoke of Cosmicism which makes that exact same point but with more flair and impact. I think Cosmicism helps illustrate what existentialism is trying to say. Cosmicism too shows that you think you are important when in fact you are not. This has implications if you assert that your life has in-built meaning and value. It too argues that you do not really make a real impact in such a big universe. Cosmicism is shamelessly materialistic. God and spirits etc are out. This can be seen as calling you a machine, a thing. But you can imagine a being being so tiny that you may as well treat it as an object for there are bigger considerations.
Lovecraft pointed out that there are too many beings for you to even register any real presence. The superstar today is nobody. The superpower is nothing. Humans have been here for countless years. The pie chart of humanity is just the one colour for the segments are too small to be seen.
And then there is animal life. You pale into complete unimportance against all the animals that are, never mind have been. And we won't mention how dolphins, chimps and whales reach the level of young human beings and thus are people.
Imagine there is a choice between you at 85 years of age being spared from dying in an avalanche at the cost of all the animals. God simply kills them all to spare you. This is hypothetical but the hypothetical scenario matters. It unravels what you are like and that counts in the real world. It shows there is a dark side to the notion that you have inherent meaning as a person and that your life is meaningful. Existing and living are not exactly the same thing. One is that you are and the other is what you are. This clarification does not affect our argument. Our point is that if you have this great value and importance then the animals have to go. Nobody really wants that to happen so if you think you are so important, be assured nobody else does. Your sense of meaning is more individualistic than you realise or admit. You tell yourself that others help you sense the meaning of your life. Obviously telling yourself that does not make it true.
Christianity claims to offer an answer for how you can have meaning in life in a universe of such great scale.
It says that God is so generous that if he decided to make just you, he could still make you a universe so big and full of animal life. And that he would do it. Yet it asserts that God is so good that if he had to die and suffer for you, he would if you were the only person alive. It says that God, despite having made many people, is doing an "as if." It is still as if it is just for you. This stuff is far from humble and shows the narcissism lurking under the Christian and religious veneer. Narcissism of that level, no matter what form it takes, would be considered a psychiatric concern.
Notice how it is instilling narcissism in you and you are doing it to yourself as well. It is projecting the narcissism in itself unto you. Maybe some will say that even if it is not narcissistic itself, it wants to be and that is what it is putting in you. It is making you a mirror of what it wants to be.
That is you the individual. Lovecraft warned that we are too biased and exaggerate how special we are. There is more. You tend to imagine that your grouping, your tribe, your family is the center of the universe. You can even expand this to all humankind.
In fact, when you say you realize all that and how small you are, and how small your nation/community is, that solves nothing. Why? Because you make the end of the world out of any disaster that happens, and that is paradoxically BECAUSE you realize that you barely register in reality. It is only in your head. You confect a drama for you want to wish the truth away.
Cosmicism advocates that you live as if you are unaware of how tiny and insignificant you are in a vast universe. In the big picture, you are nothing at all. Religion argues, though, that importance is not measured in size or impact but in how much God loves you. But that is actually saying Cosmicism is right about you being nothing. God could love a particular colony of ants first and foremost if he so chose. And they are still nothing. It is saying you need something apart from yourself to get value from. Now you are being called a parasite that seeks meaning and steals it from a host.
No matter how much a God loves you, if forces that are against you exist in this universe and he does not wipe them away, in practice you will be nothing if his plan finds that others need help more than you. You cannot think that God must organise all to suit you and your wellbeing in a world of several billion people. That is narcissism. God can make you important in his eyes but in that does not mean you will benefit from it.
If you think you are some kind of bubble in the universe that has value apart from anything else, you are wrong. You are part of the universe. You are not an island. You even have stardust in your composition. You are integrated into the universe, and it into you, so you are not a bubble of isolated or inherent meaning.
And what if this universe, as unimaginably big and empty as it is, is nothing compared to how many other universes there are out there? What if there is a set to which they all belong that is itself nothing compared to the other sets?
What if the universe is part of a multiverse? What if a replica universe is created as some physicists think every time a variation, no matter how tiny, happens in this one? What if Lovecraft is a vampire in one of these other universes?
For the purpose of argument, despite how Lovecraft denied the supernatural, what if there is? What if there are countless supernatural universes?
What if some sort of phantom child in another dimension, who would seem like a God in comparison to us, is just making our universe in an experiment? If you think that is insane and ridiculous, it is because you don't realize how much power and potential there is out there.
The point is that you get your sense of importance for you keep forgetting the true infinite scale of it all and keep acting as if you are important. Your brain lies to you to make you feel that if you suffer or are hurt that it is really important event. It feels like a total calamity to you as if the galaxy somewhere blowing up is nothing. You diminish the universe almost to nothing in order to feel you are something. It is a sort of Cosmicism in reverse.
Now we will touch on something that is rarely explored by those who think as Lovecraft did.
If your life, your existence, is as good as declared worthless, not even a speck by the universe and how big it is, the same is true for your spiritual life and spiritual existence. Nothing cares about how holy Jesus was or how holy he thought he was. Baptism is the most essential sacrament in Christianity for it allegedly wipes sins away and orientates you to God and eternal salvation. It is even more of a non-entity than you are. Your baptism is a blip even if your own life for you are not baptised continuously or repeatedly.
We all treat each other poorly a lot. It is safe to assume that if we invert Cosmicism the way we do, we will soon start treating others as dirt in order to grasp at some sense of our importance.