Most religions require a blind acceptance of their particular belief system. There is an implicit understanding that you cannot question these beliefs. This resistance to questioning shows the fundamental instability of religion. If you were truly convinced that you were right you would strongly encourage questioning. When questioning is disallowed it implies that there are embarrassing questions that cannot be answered.
Most religions, particularly the most popular ones, contain a great core of wisdom. The early creators and maintainers of the worlds religions had a huge problem though. The common people greatly needed to be taught this wisdom. The problem was that the common people were not that interested. Often they were just trying to survive. They did not have time to think about living well and being good to each other. The stewards of the religions therefore needed a hook to entice common people to look at their religion. So they created captivating stories and myths sometimes interspersed with remnants of truth and wise teachings.
Religions are also subject to gradual changes over time. Sometimes these changes are due to translation errors or even deliberate distortion. If you examine ancient religious texts, what they say is quite different from what is now being disseminated as gospel. Religious splinter groups also get created when a charismatic leader appears and distorts the original religion in order to satisfy their own needs of power and control over others. Such leaders often have personality characteristics of psychopaths, narcissists and other malignant personality disorders.
One big problem with religion is the common theme of God as creator. If there was a god that created the Universe, this implies that something must have created god and so on. This is known as the creator paradox. How can such an infinite regression exist? It’s much simpler to equate God with the Universe and nothing more. Maybe something created the Universe but how would we ever know? How can we believe in something that has no basis in fact?
Another problem with many religions is the idea of a personal god. The idea of a personal god is a myth that has been made up by ancient people long ago. A personal god is a god that created us in his image, loves us and watches over us. The belief is that if we follow his teachings and lead a good life we will be taken care of. If you don’t follow god you will endure great suffering for all eternity. The problem is that many evil people seem to lead very prosperous lives largely devoid of suffering. Many devoutly religious people in turn suffer desperate lives of misery. People and animals die brutal deaths and endure horrific torture and abuse. Often those who suffer are seen by the religious of having brought it on by themselves. How are babies supposed to follow this god’s rules though? When babies are raped, brutally murdered, tortured, die a slow and painful deaths by starvation they are to blame for this? No god that loves us and looks after us would allow such suffering of the innocent. If there was such a personal god it would be more like satan than a kind loving entity to allow such horrifying things to happen. This god appears to be in actuality a malevolent satanic entity. He is evil because he deliberately created a world in which his creations would suffer no matter what they did. Yet countless people continue to believe in the concept of a personal god. Why? They believe in this god because they were merely told this god exists. Someone told them something and they believed it without question. Without any facts or logic to support this notion of god they accept it as undeniable truth.