Theology is made to feel difficult or important via paradoxes that give it an appearance of something more mysterious than it is. (Like how ordinary movement can be made to sound impossibly difficult if you use Zeno's paradoxes.) The whole question is really quite simple to resolve if you approach it from the right direction and resist being drawn by circular questions.
OK. Here we go.
Why do people feel there is some kind of spiritual explanation of existence?
It comes down to a few things, usually:
All the above are easily dealt with if you don't allow yourself to be lured into a hall of mirrors via paradoxes.
The complex world needing a maker is the easiest to dispose of. It contains a fallacious assumption that all things must have a beginning. There are plenty of infinities all around (for example the set of all positive integers, or the calculated digits of pi, or the geometric intricacies of the mandelbrot set). The universe does not need to have been created. But let's suppose for a minute, that it was created. The same reasoning must then be applied to any creator: it must, by the same requirements have to have been created, which leads to another creator, and another, and another. This leads naturally back to an infinite regression. We are back to infinities. The universe becomes infinitely simpler to have just always been. No creator.
The soul is surprisingly easy to dispose of too. This feeling of "I" in this skull, this consciousness, is easily shown to be the action of your physical brain. As such it can't survive your body's death. How do you show that it is the action of your brain? Simple. A whole range of chemicals (alcohol, LSD, amphetamines, lithium, etc) alters the way the brain's chemistry works, and thus your consciousness. Your consciousness ceases to exist for short periods many times each night as you pass in and out of that distorted consciousness of dreaming sleep. Any time you go in for an operation in a hospital your consciousness is stopped for a time. Each time your brain's machinery moves into action afterward, producing your consciousness again. Brain injuries can radically alter your consciousness. Split brain surgery, done decades ago to stop crippling seizures of epilepsy, create two consciousnesses in the one skull. If there was a soul how could that possibly be explained? Of course some people appear to avoid the issue by saying that the soul and consciousness are two different things, but that doesn't make much sense as their original reason for believing in a soul is the consciousness -- the "I" feeling.
The meaning of life is a point that gets people really wound up. It depends upon what people understand by "meaning" or "purpose", and this is what trips people up so badly. Religion offers a way out that is really a cop-out: it suggests you leave it up to someone else. (God's purpose is unknowable by us.) But this is a mistake because it is circular thinking. Believe in god because he gives us purpose, but the only way to get that purpose is to believe in god. Much simpler and more logical is to look at what life is (we are talking about the meaning of life after all). If you start to enumerate the defining points of life you very quickly come to a very fundamental understanding of the purpose of life. Life creates more life. That is its most basic purpose. But we are a special form of life -- we are intelligent life. We have another couple of extra purposes beyond just being life-enhancing. We understand things; we are how the universe gets to understand itself! And being *social* creatures we have the need to help one another. These moral imperatives grow logically from who and what we have evolved to be. Be life-enhancing, learn and understand the world around you, and help others. There is nothing supernatural about that. No god needed.
The previous point is the best defense against the alone feeling that some worry about. I can think of nothing more uplifting than to be the way that the universe gets to know itself. And realising that I am part of this species of creatures, humankind, stumbling their often unhappy, often wonderful, way around this world makes me feel that company on all sides. Even better, our close relatives (dogs, cats, crows, parrots, dolphins, octopus, elephant fish, etc.) are our fellow travellers. As a result I'm never alone.